Outbound Email Via Exchange Online Protection When Using Hybrid Exchange Online

Posted on Leave a commentPosted in dmarc, EOP, exchange, exchange online, Exchange Online Protection, Exchange Server, hybrid, mailbox, spf

In a long term hybrid scenario, where you have Exchange Online and Exchange Server configured and mailboxes on both, internet bound email from your on-premises servers can route in two general ways.

The first is outbound via whatever you had in place before you moved to Office 365. You might have configured Exchange Online to also route via this as well.

The second is to route Exchange Server outbound emails via Exchange Online Protection. Your Exchange Online configuration does not need to be adjusted for this to work, as the default route for all domains to the internet (or the * address space as it is known) is via EOP as long as you create no alternative outbound connector for *.

This blog post looks at configuring Exchange Server so that your on-premises mailboxes also route out via Exchange Online Protection, and does it without changing the connectors made by the hybrid wizard. If you change the hybrid wizard connectors and then run the wizard again, it will reset things to how it wants them to be, which will remove your configuration changes.

This configuration setup results in a single new send connector created on-premises in Exchange Server (or one connector per site is you route emails from more than one Active Directory site). This new connector is not the Outbound to Office 365 connector that the hybrid wizard creates and so changes here do not break hybrid and changes to the hybrid wizard do not impact outbound mail flow.

This blog post also assumes you already have a working route outbound for all internet emails and you are swapping over to outbound via EOP, so these steps work though ensuring that is correct and will work before changing the route for *.

Examine the hybrid send connector to Office 365

[PS] C:\ExchangeScripts\pfToO365>Get-SendConnector out* | fl

AddressSpaces:                  {smtp:domainuk.mail.onmicrosoft.com;1}
AuthenticationCredential :
CloudServicesMailEnabled :      True
Comment : ConnectedDomains :    {}
ConnectionInactivityTimeOut :   00:10:00
DNSRoutingEnabled :             True
DomainSecureEnabled :           False
Enabled :                       True
ErrorPolicies :                 Default
ForceHELO :                     False
Fqdn :                          mail.domain.uk
FrontendProxyEnabled : 	        False
HomeMTA :                       Microsoft MTA
HomeMtaServerId :               SERVER01
Identity :                      Outbound to Office 365
IgnoreSTARTTLS :                False
IsScopedConnector :             False
IsSmtpConnector :               True
MaxMessageSize :                35 MB (36,700,160 bytes)
Name :                          Outbound to Office 365
Port :                          25
ProtocolLoggingLevel :          None
RequireOorg :                   False
RequireTLS :                    True
SmartHostAuthMechanism :        None
SmartHosts :                    {}
SmartHostsString :
SmtpMaxMessagesPerConnection :  20
SourceIPAddress :               0.0.0.0
SourceRoutingGroup :            Exchange Routing Group (DWBGZMFD01QNBJR)
SourceTransportServers :        {SERVER02, SERVER01}
TlsAuthLevel :                  DomainValidation
TlsCertificateName :            <I>CN=GlobalSign Organization Validation CA - SHA256 - G2, O=GlobalSign 
                                nv-sa, C=BE;<S>CN=*.domain.uk, O=Acme Limited, L=London, S=London, C=GB
TlsDomain :                     mail.protection.outlook.com
UseExternalDNSServersEnabled :  False

The above PowerShell from the on-premises Exchange Management Shell shows you the hybrid send connector. As you can see this is set to route emails only for your hybrid address space (domainuk.mail.onmicrosoft.com in this example)

The other important attributes for EOP mail flow here are AddressSpaces, CloudServicesMailEnabled, DNSRoutingEnabled, Fqdn, RequireTLS, SmartHosts, and TLSAuthLevel. Setting these correctly on a new send connector will allow you to route other domains to EOP and then onward to the internet.

Create a new send connector

This blog is based upon information found in https://technet.microsoft.com/en-us/library/dn751020(v=exchg.150).aspx but it differs from the scenario described there within. In this scenario, as you have already run the hybrid wizard, the connector to the cloud from on-premises and from the cloud to your servers already exists. Therefore all we need to do is create an additional send connector on-premises to route all the other domains to EOP and the internet.

New-SendConnector -Name <DescriptiveName> -AddressSpaces testdomain1.com,testdomain2.com -CloudServicesMailEnabled $true -Fqdn <CertificateHostNameValue> -RequireTLS $true -DNSRoutingEnabled $false -SmartHosts <YourDomain_MX_Value> -TlsAuthLevel  CertificateValidation -Usage Internet

In the above, the connector is originally created being able to route for two test domains (written as testdomainx.com above, comma separated in the list with no spaces). This ensures that you do not break your existing mail flow but allows you to test that the connector works and then later change the connector to support * address space. The “YourDomain_MX_Prefix” is the same value as you would use in your MX to route emails to Exchange Online (tenant-prefix-com.mail.protection.outlook.com for example).

Testing the connector

In the above new send connector, testdomain1.com is a domain hosted in a different Office 365 tenant. Testdomain2.com is a domain who’s email is not hosted in Office 365 at all. You need both test scenarios, as routing to domains inside Office 365 is more likely to work if the connector is not configured properly.

So from a mailbox on-premises, send an email to a recipient at both testdomain1.com and testdomain2.com. Do not set the connector up to use gmail or Outlook.com, as that will impact other senders within your organization. Use domains that no one else is likely to want to email.

Ensure that you do not get any NDR’s and check the recipient mailboxes to ensure delivery. Note that you are possibly likely to need to update your SPF record for the sending domain to additionally include the following:

  • include:spf.protection.outlook.com
  • ipv4:w.x.y.z (where w.x.y.z is the external IP address(es) of your on-premises Exchange transport servers)

Updating the connector

Once your mail flow tests work, and you can check the route by pasting the received message headers into http://exrca.com you should see that email routes into your Office 365 tenant, then leave EOP (the word “outbound” will be in one of the FQDNs – this server is on the external edge of EOP), then routed inbound to your email provider (or back into your recipient tenant).

Once mail flow works, you can either add more recipient domains to increase the scope of the test – for example add a domain that you email occasionally, such as the partner helping you with this work and a few other domains. Once all your testing is ready change this connector to have * as the address space and not list specific domains.

As your other connector for * is still up and running you will find that 50% of your email will use the new connector and 50% the old. Then you can disable the old connector to go 100% email outbound through EOP (you need an EOP licence per sender to do this, or if you have an Exchange Online licence for each user you are already covered).

Finally when you have been routing on-premises email through EOP for a few weeks with the old connector disabled, you can delete the old connector and tidy up the configuration rather than leaving disabled connectors around.

Duplicate Exchange Online and Exchange Server Mailboxes

Posted on 4 CommentsPosted in duplicate, EOP, exchange, exchange online, Exchange Online Protection, Exchange Server, mailbox, MX, Office 365

With a hybrid Exchange Online deployment, where you have Exchange Server on-premises and Exchange Online configured in the cloud, and utilising AADConnect to synchronize the directory, you should never find that a synced user object is configured as both a mailbox in the cloud and a mailbox on-premises.

When Active Directory is synced to Azure Active Directory, the ExchangeGUID attribute for the on-premises user is synced to the cloud (assuming that you have not do a limited attribute sync and not synced the Exchange attributes – as that is required for Exchange Online hybrid). The Exchange Online directory takes a sync of information relating to Exchange from Azure Active Directory (Azure AD), which is known as forward sync. This ensures that the ExchangeGUID attribute from the on-premises mailbox is synced into your Exchange Online directory.

When a user is given an Exchange Online licence, it becomes the job of Exchange Online to provision a mailbox for this user. When Exchange Online needs to provision a new mailbox, it will not do so where the ExchangeGUID attribute already exists. The existence of this attribute tells the provisioning process that the mailbox already exists on-premises and will be migrated here later and so not to create a conflicting mailbox. A cloud user who does not have an ExchangeGUID attribute synced from on-premises will get a mailbox created by the Exchange Online provisioning process upon a licence being assigned, and on-premises users that do not have a mailbox on-premises (who also have no ExchangeGUID attribute) will also find that granting them an Exchange Online licence will trigger the creation of a mailbox for them.

This is all well and good, and the above is what happens in most cases. But there is an edge case where an on-premises user with a mailbox (and therefore has the ExchangeGUID attribute populated) will also get a mailbox in Exchange Online. This happens where the organization manually created cloud mailboxes before enabling AADConnect to sync the directories, and these cloud users match the on-premises user by UserPrincipalName and they are given an Exchange Online licence.

In this above case, because they are cloud users with an Exchange Online licence they get a mailbox. Deleting the cloud user and then enabling sync will cause the original mailbox to be restored to the user account as the UserPrincipalName matches.

For example, the below shows a user being created in the cloud called “twomailboxes@domain.com”:

image

The user is granted a full Office 365 E3 licence, so this means the user has an Exchange Online mailbox. There is no AADConnect sync in place, but the UPN matches a user on-premises who has a mailbox.

In Exchange Online PowerShell, once the mailbox is provisioned we can see the following:

image

PS> get-mailbox twomailboxes | fl name,userprincipalname,exchangeguid



Name              : twomailboxes
UserPrincipalName : twomailboxes@domain.com
ExchangeGuid      : d893372b-bfe0-4833-9905-eb497bb81de4

Repeating the same on-premises will show a separate user (remember, no AD sync in place at this time) with the same UPN and a different ExchangeGUID.

image

[PS] >get-mailbox twomailboxes | fl name,userprincipalname,exchangeguid



Name              : Two Mailboxes
UserPrincipalName : twomailboxes@cwh.org.uk
ExchangeGuid      : 625d70aa-82ed-47a2-afa2-d3c091d149aa

Note that the on-premises object ExchangeGUID is not the same as the cloud ExchangeGUID. This is because there are two seperate mailboxes.

Get-User in the cloud will also report something useful. It will show the “PreviousRecipientTypeDetails” value, which is not modifiable by the administrator, in this case shows there was not a previous mailbox for the user but this can show that a previous mailbox did exist. For completion we also show the licence state:

image

PS > get-user twomailboxes | fl name,recipienttype,previousrecipienttypedetails,*sku*



Name                         : twomailboxes
RecipientType                : UserMailbox
PreviousRecipientTypeDetails : None
SKUAssigned                  : True

Now in preparation for the sync of the Active Directory to Azure Active Directory, the user accounts in the cloud are either left in place (and so sync will do a soft-match for those users) or they are deleted and the on-premises user account syncs to the cloud. In the first case, the clash on the sync will result in the cloud mailbox being merged into the settings from the on-premises mailbox. In the second case, there is no user account to merge into, but there is a mailbox to restore against this user. And even though the newly synced user has an ExchangeGUID attribute on-premises that is synced to the cloud, and they have a valid licence, Exchange Online reattaches the old mailbox associated with a different GUID.

The impact of this is minor to massive. In the scenario where MX points to on-premises and you have not yet moved any mailboxes to the cloud, this cloud mailbox will only get email from other cloud mailboxes in your tenant (there are none in this scenario) or internal alerts in Office 365 (and these are reducing over time, as they start to follow correct routing). It can be a major issue though if you use MX to Exchange Online Protection. As there is now a mailbox in the cloud for a user on-premises, inbound internet sourced email for your on-premises user will get delivered to the cloud mailbox and not appear on-premises. Where the invalid mailbox has no email, recovery is not required. Finally, where there is a duplicate mailbox, move requests for those users for onboarding to Exchange Online will fail:

image

This reads “a subscription for the migration user <email> couldn’t be loaded”. This occurs where the user was not licenced and so there was not a duplicate mailbox in the cloud, but the user was later licenced before the migration completed.

Where the invalid duplicate mailbox exists in the cloud and is getting valid emails delivered to it, the recovery work described below additionally will involve exporting email from this invalid mailbox and then removing the mailbox as part of the fix. Extraction of email from the duplicate mailbox needs to happen before the licence is removed.

To remove the cloud mailbox and to stop it being recreated, you need to ensure that the synced user does not have an Exchange Online licence. You can grant them other licences in Office 365, but not Exchange Online. I have noticed that if you do licencing via Azure AD group based licencing rules then this will also fail (these are still in preview at time of writing) and that you need to ensure that the user is assigned the licence directly in the Office 365 portal and that they do not get the Exchange Online licence. After licence reconciliation in the cloud occurs (a few minutes typically) the duplicate mailbox is removed (though I have seen this take a few hours). The Get-User cmdlet above will show the RecipientType being a MailUser and not Mailbox.

You are now in a position where your duplicate cloud mailbox is gone (which is why if that mailbox had been a target to valid emails before now, you would need to have extracted the data via discovery and search processes first).

Running the above Get-User and Get-Mailbox (and now Get-MailUser) cmdlets in the cloud will show you that the ExchangeGUID on the cloud object now matches the on-premises object and the duplication is gone. You can now migrate that mailbox to the cloud successfully.

We can take a look at what we see in remote PowerShell here:

Recall from above that there were two different ExchangeGUIDs, one in the cloud and one on-premises. These in my example where:

Cloud duplicate ExchangeGuid      : d893372b-bfe0-4833-9905-eb497bb81de4

On-premises mailbox ExchangeGuid  : 625d70aa-82ed-47a2-afa2-d3c091d149aa

Get-User before licences removed in the cloud, showing a mailbox and that it was previously a mailbox as well:

image

PS > get-user twomailboxes | fl name,recipienttype,previousrecipienttypedetails,*sku*



Name                         : Two Mailboxes
RecipientType                : UserMailbox
PreviousRecipientTypeDetails : UserMailbox
SKUAssigned                  : True

Get-Mailbox in the cloud showing the GUID was different from on-premises:

image

PS > get-mailbox twomailboxes | fl name,userprincipalname,exchangeguid



Name              : Two Mailboxes
UserPrincipalName :
twomailboxes@domain.com

ExchangeGuid      : d893372b-bfe0-4833-9905-eb497bb81de4

Once the licence is removed in Office 365 for Exchange Online and licence reconciliation completes (SKUAssigned is False) you will see that Get-User shows it is not a mailbox anymore:

image

PS > get-user twomailboxes | fl name,recipienttype,previousrecipienttypedetails,*sku*



Name                         : Two Mailboxes
RecipientType                : MailUser
PreviousRecipientTypeDetails : UserMailbox
SKUAssigned                  : False

And finally Get-MailUser (not Get-Mailbox now) shows the ExchangeGUID matches the on-premises, synced, ExchangeGUID value:

image

PS > get-mailuser twomailboxes | fl name,userprincipalname,exchangeguid



Name              : Two Mailboxes
UserPrincipalName : twomailboxes@domain.com
ExchangeGuid      : 625d70aa-82ed-47a2-afa2-d3c091d149aa

Note that giving these users back their Exchange Online licence will revert all of the above and restore their old mailbox. As these users cannot have an Exchange Online licence assigned in the cloud, for risk of their old mailbox returning you need to ensure that within 30 days of their on-premises mailbox being migrated to the cloud you do give then an Exchange Online mailbox. Giving them a licence after migration of their on-premises mailbox to the cloud will ensure their single, migrated, mailbox remains in Exchange Online. But giving their user a licence before migration will restore their old cloud mailbox.

For users that never had a matching UPN in the cloud and a cloud mailbox, you can licence them before you migrate their mailbox as they will work correctly within the provisioning system in Exchange Online.

Conversation Red Number in Skype For Business That Won’t Go Away

Posted on Leave a commentPosted in conversation, exchange online, Exchange Server, Outlook, Skype For Business Online, Skype for Business Server

I have had this issue for ages, but could not find any answer for it on the internet that did not involve resetting Skype for Business or other complex stuff when in fact the answer is so easy it hurts! Finding it was one of those Duh! moments.

You have this:

image

Skype for Business shows a red flag in one of the sections that will not go away. In my case it was the Conversation History pane and all the conversations in the view were read!

Then one day in Outlook I noticed the Missed Conversations view in Outlook:

image

Its a Search View and it was already active for me, but look – it also says one conversation. So I scrolled down the list of conversations in Outlook, found the unread one and the issue went away in Skype for Business within seconds.

image

image

This issue will probably be true for Teams as well when Outlook Conversation History functionality moves over to that product as well from Skype for Business Online

Office 365 and ACDC

Posted on Leave a commentPosted in acdc, anycast, cafe, exchange online, Exchange Server, networking, Office 365

The best connectivity to Office 365 is achieved with local internet breakout and local DNS egress. This means things like each branch office should connect directly to the internet and not via the Head Office and then to the internet and that DNS lookups are done local as well. The reason for DNS lookups is to do with AnyCast and DNS resolution. Microsoft see where you make your DNS requests from and return responses to Office 365 that are near where the DNS egress point is. So if you lookup DNS from the head office in a different county, but still have local internet breakout, you might connect to the Office 365 endpoints close to the head office and not the endpoints in your country.

To test this, it used to be the case that you could ping outlook.office365.com and see what FQDN was returned and ensure that it was in the same geography to where you are. At the time of writing this is still the case some of the time, but it is changing.

Therefore, lets say you were located in Europe and you ran “ping outlook.office365.com” – it might return something in the URL that looked like EMEA-WEST. If it returned US anything then you had an issue with DNS and maybe internet egress. An example of how it always used to be was:

image

This was a great test until recently, but in the last few months this DNS lookup has changed to connect to an endpoint called ACDC. For example now it might show:

image

This is a connection to the ACDC endpoint, which is AnyCast DNS Cafe, where Cafe is the Client Access Front End service, or the Front Door service to Exchange Online. Not the data location, but a service endpoint close to you to do SSL connectivity and work out where your mailbox is and to connect to that endpoint. In the last year by changing to the ACDC endpoint technology, Microsoft have reduced latency to cloud hosted Exchange Online in the region of 100ms.

Unfortunately this means a simple test for local internet egress has stopped working and you need to investigate further the route taken to reach the Microsoft network. A suggestion simple test for this is tracert. For this you need to run “tracert outlook.office365.com”. This has the risk of being blocked at the firewall, as ICMP is often restricted even though it is used to help modulate TCP window size and other useful network packet adjustments, but an idea can be got from running tracert to the same location as the ping.

For example, ping outlook.office365.com for me was returning an RTT (round trip time) of 17ms. Tracert showed similar:

image

In my case I was getting the following:

Tracing route to outlook.ms-acdc.office.com [40.101.72.194]
over a maximum of 30 hops:

  1     1 ms    <1 ms     2 ms  192.168.0.1
   2     1 ms     2 ms     1 ms  192.168.5.1
   3     *        *        *     Request timed out.
   4     9 ms     9 ms     9 ms  oxfd-core-2a-xe-003-0.network.virginmedia.net [62.254.128.161]
   5     *        *        *     Request timed out.
   6     *        *        *     Request timed out.
   7    12 ms    11 ms    13 ms  tcma-ic-2-ae9-0.network.virginmedia.net [62.253.174.178]
   8    12 ms    12 ms    12 ms  213.104.85.230
   9    20 ms    20 ms    19 ms  be-71-0.ibr02.dbb.ntwk.msn.net [104.44.9.180]
  10    19 ms    18 ms    18 ms  104.44.10.150
  11     *        *        *     Request timed out.
  12     *        *        *     Request timed out.
  13     *        *        *     Request timed out.
  14     *        *        *     Request timed out.
  15    22 ms    17 ms    18 ms  40.101.72.194


Trace complete.

From this we can see 18ms to the first hop on Microsoft’s network. Full RTT and latency for Outlook can be found on the Connection Status dialog, as this includes the processor time in Exchange Server/Exchange Online and the network RTT to the server that contains the data and not just the Microsoft Front Door CAFE service.

DMARC Quarantine Issues

Posted on Leave a commentPosted in dkim, dmarc, EOP, exchange, exchange online, Exchange Online Protection, Exchange Server, spf, spoof

I saw the following error with a client the other day when sending emails from the client to any of the Virgin Media owned consumer ISP email addresses (virginmedia.com, ntlworld.com, blueyonder.com etc.)

mx3.mnd.ukmail.iss.as9143.net gave this error:
vLkg1v00o2hp5bc01Lkg9w DMARC validation failed with result 3.00:quarantine

In the above, the server name (…as9143.net) might change as will the value before the error, but either DMARC validation failed with result 3.00:quarantine or 4.00:reject is the end of the error message.

We resolved this error by shorting the DMARC record of the sending organization. Before we made the change we had a DMARC record of 204 characters. We cannot find a reference online to the maximum length of a DMARC record, though we could successfully add a record of this length to Route 53 DNS provided by AWS, though a record of 277 characters was not allowed in AWS. Other references online to domain character length seem to imply that 255 characters is the max, but not specifically for DMARC.

So, shortening the DMARC record to remove two of the three email addresses in each of the RUA and RUF values was the fix that we needed. This change was done for two reasons, first the above error occurred only with emails to Virgin Media and sometimes an NDR would be received and other times the NDR would fail, but the original email never made it through and secondly the two removed email addresses where not actively being checked for DMARC status messages anyway and so there is no harm in the removal of them from the DMARC record anyway!

The original DMARC record we had this issue with looked like this (xxx.xxxxx representing the client domain):

v=DMARC1; p=quarantine; fo=1;rua=mailto:admin@xxx.xxxxx,mailto:dmarc-rua@dmarc.service.gov.uk,mailto:dmarc@xxx.xxxxx;ruf=mailto:admin@xxx.xxxxx,mailto:dmarc-ruf@dmarc.service.gov.uk,mailto:dmarc@xxx.xxxxx;

Then we changed the record to the following to resolve it:

v=DMARC1; p=quarantine; fo=1;rua=mailto:dmarc-rua@dmarc.service.gov.uk;ruf=mailto:dmarc-ruf@dmarc.service.gov.uk;

Reducing the length of the record resulted in DMARC analytics and forensic email not going to mailboxes at the client (one of whom those mailboxes did not exist anyway) and only going to the UK government DMARC policy checking service, but most importantly for a client that has a requirement to respond to citizen’s emails (and whom could easily be using Virgin Media email addresses) we resolved the issue.

On-Premises Public Folders, Exchange Online, And Multiple Forests

Posted on 4 CommentsPosted in exchange online, Exchange Server, Office 365, Public Folders

Here is a scenario I have come across in a few clients in just the last few weeks. This is not something that I recommend implementing lightly, as there are implications. But it does allow some very specific problems with public folder integration to be solved in the short term.

The specifics of the scenario is that with Exchange Online mailboxes and on-premises public folders, each user in Exchange Online needs a login account in the on-premises forest. That is easy for hybrid mode Exchange Server to Exchange Online, but once you move to multi-forest hybrid it is not. In multi-forest hybrid you will have users from more than one forest (of course).

When you set up integration between Exchange Online and an on-premises Exchange organization, you choose the single organization that you can proxy public folder requests to. This is done with Set-OrganizationConfiguration in Exchange Online and the value is the email address(es) of mailboxes that are located on the same servers as the public folder servers on premises – these are known as the public folder proxy mailboxes. For example this would look like Set-OrganizationConfiguration -PublicFoldersEnabled Remote -RemotePublicFolderMailboxes pfProxy1. Once this is done, all Exchange Online users get allocated one of these email addresses as their public folder proxy address. When the user uses Outlook, the AutoDiscover response for their mailbox will include a publicFolder value that contains this email address given to the users mailbox. For example, it would look like this:

      <PublicFolderInformation>

        <SmtpAddress>pfProxy1@domain.com</SmtpAddress>

      </PublicFolderInformation>

Outlook will then do AutoDiscover for that mailbox (in the same way that it does AutoDiscover for shared mailboxes) and attempt to login to the public folders (Outlook 2010) or show “Public Folders” in the Outlook tree folder view and wait until the user expands to attempt to connect (Outlook 2013 and later). If the user has an account on-premises then the Public Folder hierarchy is shown and the user can open folders for which he or she has permission.

But, if the user belongs to another forest, they do not have an account in the forest that the public folders are in and so login to the public folder hierarchy fails.

image

So how do we solve this. There is one way I have tested, and another way I have yet to test. The first way turns off the public folders for the users in all the non-primary forest for public folders. They cannot access public folders at all, unless you implement a third party folder migration software and even these might not work. The steps to implement this “fix” is to begin to implement public folder migration, but actually to stop very early in the process and jump to near the end of that process. So first create a new public folder in Exchange Online. As you are using public folder proxies, you can only create public folders that are held for migration, and that is the key to this idea. So New-Mailbox pfMailbox1 -PublicFolder -HoldForMigration will create a new empty (and that is important) public folder mailbox in Exchange Online. Now near the end of published process for public folder migration there is a step where you can individually set cloud mailboxes to use the cloud public folders. You do this with Set-Mailbox name -DefaultPublicFolderMailbox pfMailbox1 and this user will now only look at the empty cloud public folders and not attempt to connect on-premises. Therefore if you do this for all mailboxes from the non-primary forest for public folders then they will stop failing to login on-premises. Sure, they loose public folder access to their original folders as well, but that was the risk that that you would have been discussing with your consultant before you started migrating.

My second, untested option, is to instead run the Set-OrganizationConfiguration option but to use proxy mailboxes from multiple forests that have previously created and synced. And rather than allowing Exchange Online to randomly distribute the proxy mailboxes across all the users, you would provision the user with the correct proxy mailbox for the organization they are in. Assume therefore that Forest1 has pfForest1Proxy and Forest2 has pfForest2Proxy1. You would run Set-OrganizationConfiguration -PublicFoldersEnabled Remote -RemotePublicFolderMailboxes pfForest1Proxy,pfForest2Proxy and then individually ensure that Set-Mailbox <each user in Forest1> -DefaultPublicFolderMailbox pfForest1Proxy and that Set-Mailbox <each user in Forest2> -DefaultPublicFolderMailbox pfForest2Proxy. Note that this is not tested. Please let me know if this works for you in the comments if I don’t get to test it first!

Forcing Transport Level Secure Email With Exchange Online

Posted on Leave a commentPosted in EOP, exchange online, Exchange Online Protection, Exchange Server, Office 365, security, starttls, TLS

In Exchange Online there are a few different options for forcing email to require an encrypted connection. These depend upon the level of licence you have, and some of them are user based (Office 365 Message Encryption for example), but there are two ways to force TLS (transport layer security) for the email between when the message leaves Office 365 and arrives with the recipient email system.

The first of these is a Mail Flow rule, and the second of these is a Conditional Connector. Only the second of these works!

The first, just for clarity, appears to work but it is not 100% reliable and will end up with stuck emails unless you configure the rule 100% correct. The second option is the recommended option ongoing.

For completion, we will also look at forcing TLS inbound to Exchange Online

Force TLS with Mail Flow Rules

This option relies on a Transport Rule (or mail flow rule) setting called “Require TLS”. This below example shows a UK Government requirement that states that emails to certain government departments (by domain name) should enforce the use of TLS:

image

This rule uses the condition “if the recipient address includes” and the list of UK Government domains that should be secured. This list is found at https://www.gov.uk/guidance/set-up-government-email-services-securely#configure-cloud-or-internet-based-email-services and for test purposes I have added my own domains to the list. The action for this rule is “to require TLS encryption”.

As mentioned above, this rule is not 100% reliable, and the the issue is when you have a Hybrid Exchange Online environment back to on-premises Exchange, though that connector back to on-premises uses TLS, the rule to force TLS conflicts and the email stays in Exchange Online in a pending state and is never delivered.
To avoid this issue, an exception is required to the rule to exempt it for your on-premises domains.

Force TLS with Conditional Connectors

This is the recommended route for forcing TLS. It requires two settings created. The first is a Conditional Connector as shown:

image

You must select “Only when I have a transport rule set up that redirects messages to this connector” on the connector use page.

image

MX delivery is the most likely option, and then either any digital certificate or issued by a trusted third party depending upon your requirements.

image

If you have more than one domain to force TLS to, then do not enter the end certificate info here, as it will be different for each domain.

Now that you have the connector in place, which will only be used is rules route the emails to that connector, you can create the rule.

image

We have purposely excluded the domains we had an issue with when using “Require TLS”, but Microsoft say that workaround should not be needed – I will update this post once I know that for sure! Also, as the rule shown in the screenshots adds a disclaimer so that we can check that the rule is being executed.

Inbound Required TLS with Connectors

To force inbound TLS requirements, so that email from given domains are rejected if they do not open a TLS session with your organization to send an email you create a Partner to Office 365 connector. This connector will force TLS or reject the email inbound if that cannot happen:

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And then choosing “Reject email messages if they aren’t sent over TLS” as part of the connector conditions:

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XOORG, Edge and Exchange 2010 Hybrid

Posted on 2 CommentsPosted in 2010, Edge, EOP, exchange, exchange online, Exchange Online Protection, Exchange Server, Office 365

So you have found yourself in the position of moving to Exchange Online from a legacy version of Exchange Server, namely Exchange 2010. You are planning to move everyone, or mostly everyone to Exchange Online and directory synchronization plays a major part (can it play a minor part?) in your plans. So you have made the option to go hybrid mode when you discover that there are manual steps to making Exchange 2010 mail flow to Exchange Online work if you have Exchange Edge Servers in use.

So, what do you do. You look online and find a number of references to setting up XOORG, but nothing about what that is and nothing about what you really need to do. And this you found this article!

So, how do you configure Exchange Server 2010 with Edge Servers, so that you can have hybrid mode to Exchange Online.

Why You Need These Steps

So you ran the hybrid wizard, and it completed (eventually if you have a large number of users) and you start your testing only to find that emails never arrive in Office 365 whilst your MX record is still pointing on-premises. After a while you start to get NDR’s for your test emails saying “#554 5.4.6 Hop count exceeded – possible mail loop” and when you look at the diagnostic information for administrators at the bottom of the NDR you see that your email goes between the hub transport servers and the edge servers and back to the hub transport servers etc. and about three or so hours after sending it, with the various timeouts involved, the email NDR arrives and the message is not sent.

The problem is that the Edge Server sees the recipient as internal, and not in the cloud, as the email has been forwarded to the user@tenant.mail.onmicrosoft.com, and Exchange 2010 is authoritative for this namespace. You are missing a configuration that tells the Edge that some emails with certain properties are not internal, but really external and others (those coming back from the cloud) are the only ones to send internal to the on-premises servers.

So what do you do?

Preparation

Before you run the hybrid wizard you need to do the following. If you have already run the wizard that is fine, you will do these steps and run it again.

  1. Install a digital certificate on all your Edge Servers that is issued by a trusted third party (i.e. GoDaddy, Digicert and others). The private key for this certificate needs to be on each server as well, but you do not need to allow the key to be exported again.
  2. Enable the certificate for SMTP, but ensure you do not set it as the default certificate. You do this by using Exchange Management Shell to Get-ExchangeCertificate to key the key’s thumbprint value and then running Enable-ExchangeCertificate –Thumbrint <thumbprintvalue> –Services SMTP. At this point you are prompted if you want to set this certificate as the default certificate. The answer is always No!
  3. If you answer yes, then run the Enable-ExchangeCertificate cmdlet again, but this time for the certificate thumbprint that was the default and set the default back again. If you change the default you will break EdgeSync and internal mail flow for everyone. And you must use the self-signed certificate for EdgeSync and this third party issued certificate for cloud mail flow, as you cannot use the same certificate for both internal and external traffic.
  4. The certificate needs to be the same across all your Edge Servers.
  5. If you are doing multi-forest hybrid, then the certificate is only the same across all the Edge Servers in one Exchange Organization. The next organization in your multi-forest hybrid needs to use a different certificate for all its Edge Servers.
  6. Then take this same certificate and install it on a single Hub Transport server on-premises. The hybrid wizard cannot see what certificates you have on the Edge Servers, so you need to help the wizard along a bit. Again, this certificate needs enabling for SMTP, but not setting as the default certificate.

Running The Hybrid Wizard

Now you can run the hybrid wizard. The important answers you need to include here are that the hub transport server that you pick must be the one that you placed the certificate on, as you cannot pick the Edge Servers that you will use for mail flow in the wizard. But you will need to enter the IP addresses that your Edge Servers are published on the internet as, and you will need to enter the FQDN of the Edge Servers as well.

Complete the wizard and then time for some manual changes.

Manual Changes

The hybrid wizard will have made a send connector on-premises called “Outbound to Office 365”. You need to change this connector to use the Edge Servers as the source servers. Note that if you run the hybrid wizard again, you might need to reset this value back to the Edge Servers. So once all these required changes are made, remember that running the wizard again could constitute an unexpected change and so should be run with care or out of hours.

Use Set-SendConnector “Outbound to Office 365” -SourceTransportServers <EDGE1>,<EDGE2> and this will cause the send connector settings to replicate to the Edge Server.

Next get a copy of the FQDN value from the receive connector that the hybrid wizard created on the hub transport server. This receive connector will be called “Inbound from Office 365” and will be tied to the public IP ranged of Exchange Online Protection. As your Edge Servers receive the inbound emails from EOP, this receive connector will serve no purposes apart from the fact that its settings are the template for your receive connector on the Edge Servers that the wizard cannot modify. The same receive connector will also have a setting called TlsDomainCapabilities and the value of this setting will be mail.protection.outlook.com:AcceptOorgProtocol. AcceptOorgProtocol is the XOORG value that you see referenced on the internet, but it is really called AcceptOorgProtocol and this is the value that allows the Edge Server to distinguish between inbound and outbound mail for your Office 365 tenant.

So on each Edge Server run the following cmdlet in Exchange Management Shell to modify the default receive connector: Set-ReceiveConnector *def* -TlsDomainCapabilities mail.protection.outlook.com:AcceptOorgProtocol -Fqdn <fqdnFromTheInboundReceiveConnectorOnTheHubTransportServer>.

This needs repeating on each Edge Server. The FQDN value ensures that the correct certificate is selected and the TlsDomainCapabilities setting ensures you do not loop email to Office 365 back on-premises again. Other emails using the Default Receive Connector are not affected by this change, apart from now being able to offer the public certificate as well to their inbound partners.

You can now continue with your testing knowing that mail flow is working, so now onto AutoDiscover, clients, free/busy, public folders etc. etc. etc.

Capax Zantas EAS EWS 501 Errors

Posted on Leave a commentPosted in EAS, Exchange Server, Kemp, Load Master, Zantas

Whilst load balancing Exchange 2013 with a Capax Zantas EAS deployment in place I was reminded of an issue I experienced a few years ago with a Kemp load balancer. The EAS app for OWA was failing with various errors such as:

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Communication with service failed. The service might be down or misconfigured. Error code: 500

As well as the search functionality never returning results.

And in the EASOWABackend log file we were seeing the following:

w3wp.exe Error: 0 : 22 : [09/23/2016 10:13:22.880 AM] User username@domain.com: EWS Call failed Microsoft.Exchange.WebServices.Data.ServiceRequestException: The request failed. The remote server returned an error: (501) Not Implemented. —> System.Net.WebException: The remote server returned an error: (501) Not Implemented.
   at System.Net.HttpWebRequest.GetResponse()
   at Microsoft.Exchange.WebServices.Data.EwsHttpWebRequest.Microsoft.Exchange.WebServices.Data.IEwsHttpWebRequest.GetResponse()
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.GetEwsHttpWebResponse(IEwsHttpWebRequest request)
   — End of inner exception stack trace —
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.GetEwsHttpWebResponse(IEwsHttpWebRequest request)
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.ValidateAndEmitRequest(IEwsHttpWebRequest& request)
   at Microsoft.Exchange.WebServices.Data.MultiResponseServiceRequest`1.Execute()
   at Microsoft.Exchange.WebServices.Data.ExchangeService.InternalConvertIds(IEnumerable`1 ids, IdFormat destinationFormat, ServiceErrorHandling errorHandling)
   at Microsoft.Exchange.WebServices.Data.ExchangeService.ConvertId(AlternateIdBase id, IdFormat destinationFormat)
   at EASOWA2013.EASOWABackend.OpenMessage(String owaID, String userEmail, String authToken, String pageURL)

This error contained a 501 Not Implemented message, and this message was getting exposed in OWA. But this error was not present in any of the Exchange Server logs, so it was not being caused by Exchange. This led us to looking at the load balancer, and testing EAS when bypassing the load balancer. To bypass the load balancer requires host file changes and changing the EAS configuration, so it is not a trivial change. When the load balancer was out of the traffic path everything worked fine.

Under the Kemp system logging (Logging Options > System Log Files > System Message File) we were seeing:

Sep 22 16:39:09 cwh-kemp01 kernel: L7: badrequest-client_read [192.168.x.y:44987->192.168.lb.vip:443] (-501): 192.168.lb.vip:443] (-501): 192.168.lb.vip:443] (-501): 192.168.lb.vip:443] (-501): 192.168.lb.vip:443] (-501): 192.168.lb.vip:443] (-501): 192.168.lb.vip:443] (-501): 192.168.lb.vip:443] (-501): 192.168.lb.vip:443] (-501): 192.168.lb.vip:443] (-501): 192.168.lb.vip:443] (-501):

Where 192.168.x.y was the client IP and 192.168.lb.vip was the load balanced IP for Exchange.

With reference to the above linked article, the fix was to change the Kemp’s handling of the 100-Continue feature and by changing the setting to RFC-7231 Compliant EAS in OWA started working:

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Photos, Exchange, And The File System

Posted on 1 CommentPosted in 2013, 2016, Exchange Server, Office 365, owa

On an Exchange 2013 and later server this is a folder called photos that gets created after installation and can contain a couple of user photos for some of your users. How does it get there and what does it contain?

The photos folder appears (on 2016 anyway) when the user uploads a photo (via OWA). Two images are created one 96square and the other 648square. They are made in a folder unique to the user and on the mailbox server that contains their active mailbox at the time of upload.

To reproduce this, login to OWA. Determine which server is currently the active server for that mailbox and then access the file system of that server. You are looking for “C:\Program Files\Microsoft\Exchange Server\V15\ClientAccess” though it will be wherever Exchange Server was installed if not the C: drive. If anyone has uploaded photos already via this server then you will see a folder named photo. You can delete this folder without impact (unless someone is actively uploading a photo at that exact time).

In OWA, click the photo icon top right and then click Change:

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Click Upload photo and select a photo. I’ve used the sample pictures that are installed on Windows 7 in this example:

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At this point a copy of the photo is uploaded to a web service on Exchange Server. Click Save above your chosen photo. At this point the photo folder in the ClientAccess folder on the server that is active for your mailbox is created. Inside this folder you will see a subfolder called _domain.com-UNIQUEID. Inside this folder will be two subfolders called HR96x96 and HR648x648. Inside each of these will be the JPEG file that was created at the time of saving the upload. The size of each will match the folder name and the name of the file will be _Alias-UNIQUEID. If the user deletes their photo then a 0 byte JPEG file will be created in the folder.

Note that these two photos are not a cache of the photo for the Exchange Server to download to other users. They are just used during uploading the photos. Once uploaded they are resized using this file system location and then stored in their respective locations. The 96×96 photo (at less than 100Kb) is stored in the Active Directory and the 648×648 image is stored in the Exchange 2013 or later mailbox for use by Exchange, Skype for Business and SharePoint.

If there are policies and privacy laws that state the caching of images on the file system must be avoided, then you should be able to delete the photo upload cache at your convenience.

The photo folder does not appear on another server when viewing that user with a photo in their mailbox. Requesting the photo is done via owa/service.svc and not AFAIK from a file on the file system.

Deleting the folder after the fact did not impact my test users photo (as its now in the mailbox and not read from the file system). If this mailbox is later migrated to Office 365, then the photo will migrate with the mailbox as it is part of the mailbox. If the photo stored in AD is less than 100kb then it will be synced to Azure AD.