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Exchange Online Warning On Receipt Of New Email Sender

Released recently to no fanfare at all, Microsoft now has a SafetyTip that appears if you receive email from a first time recipient.

Most often phish emails will come from an address you have never received email from before, and sometimes this email will try to impersonate people you communicate with or are internal to your organization. Warning for attempted spoofed domains or users is part of Microsoft Defender for Office 365 (previously known as Advanced Threat Protection for Office 365) and the functionality to warn based on similar sender is also part of this product if you enable the “mailbox intelligence” option. But the option to warning for a new sender is available for all Exchange Online users without ATP licences.

The user sees the SafetyTip above the email body as shown below once this new feature is enabled:

New Sender Safety Tip

To turn on this option you enable a custom message header in a transport rule and then within 30 minutes or so, every new sender under the scope of the rule is warned when they receive email from a new sender. This also includes senders that have not send a lot of message to you, as I see that this Safety Tip appear on subsequent messages from the same sender. Not sure yet when this stops appearing for slightly less new senders!

To enable this feature create the following transport rule, restricting the scope of the rule to some users only to start with and then when happy with the functionality changing the rule to apply to all users.

First Contact Safety Tip Transport Rule

Open Exchange Online Control Panel (at the time of writing this is in the old UX for this, so these screenshots represent the classic view – this will change at some point in the future) and select Mail Flow > Rules

Click the + icon > Modify Messages and fill in the name “Enable First Contact Safety Tip”

Select under Apply this rule if… The sender is located > Outside the organization

Select under Do the following… Set the message header to this value and click the first option for Enter text and copy and paste the following string X-MS-Exchange-EnableFirstContactSafetyTip

Click the second option for Enter text and enter any value you like. I have had reports that only “enable” works but that is not my experience and I had this working with the value AnythingYouLike!

I turn off the audit option and then save the rule as shown:

New Transport Rule for First Contact Safety Tip

To set the rule for a pilot program, click More options and then the newly displayed add condition button and then select that the rule should only apply if the recipient is and select a few names from your global address list.

Pilot Program for First Contact Safety Tip

Within 30 minutes and then the next new sender and Outlook, Outlook Web Access and Outlook Mobile will display the new safety tip

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MFA and End User Impacts

This article will look at the various different MFA settings found in Azure AD (which controls MFA for Office 365 and other SaaS services) and how those decisions impact users.

There is lots on the internet on enabling MFA, and lots on what that looks like for the user – but nothing I could see that directly laid out all the options and the impact of each option.

The options that the admin can set that I will cover in this article are:

  • Default settings for the MFA registration service
  • The enhanced registration service (now depreciated)
  • The refreshed enhanced registration service (MFA and Self-Service Password Reset registration combined)

The general impact to the user is that the user needs to provide a second factor to login. In this article I will not detail the above registration for each of the second factors and only cover the general process of registration – your exact experience on registration will depend upon what second factors (app notifications, app code, phone call and text message) you choose to implement.

This article will look mainly at the different between having no MFA and what happens from the users perspective as the admin turns on a requirement to have MFA. The various options that the admin can use to enable MFA are as follows:

  • Office 365 MFA (aka the legacy method) that is available to all users with or without a licence
  • Azure AD Conditional Access and setting a rule that requires MFA (when the user is not registered)
  • Azure AD Premium 2 licence and MFA Registration (register without requiring MFA to be enabled)
  • Azure AD Free fixed Conditional Access rules (MFA for all users) which is in preview at the time of writing (Aug 2019)

Terminology and Settings

This article refers back to a series of different settings in each of the following sections. To make the article avoid repeating itself, this section outlines each of the general settings, what I mean by the description I use and where I turn that setting on or off.

Office 365 MFA – This is the legacy MFA options set via > User Management > Multi-Factor Authentication. This user experience turns on or off MFA for users regardless of app or location (unlike Conditional Access) and has settings for the different second factor methods (for example you can disable SMS from here).

Legacy MFA Admin Page

Conditional Access Based MFA – This is where you set rules for accessing cloud apps based on the user, the location, the risk (P2 licence required), the device (domain joined or compliant), the location (IP), the device risk (MDATP licence required), compliance (Intune required) etc. If you rule requires MFA and the logging in user passes the requirements for this rule (and is not otherwise blocked) then this is what I call Conditional Access Based MFA. This is set in > Azure Active Directory > Enterprise Applications > Conditional Access

Conditional Access Based MFA

Azure AD Premium 2 MFA Registration – This is where you can get users to register before you turn on MFA via either of the above routes. Without the P2 licence you turn on MFA and at the next login the user needs to register. With P2 you can turn on registration at login without forcing MFA. You would then enable MFA later or you can have registration at next login (and defer that by 14 days) so that the user registers even if they never hit an endpoint that the need to do MFA on. For example, MFA when external and the user never works remotely. Therefore they will never have to do MFA and therefore never be required to register – which P2 licence you can get them to register independent of the requirement to do MFA. You access these settings via > Azure AD Identity Protection > MFA Registration

Azure AD P2 MFA Registration

Self Service Password Reset Registration – This is shown if the user is in scope for SSPR and SSPR is enabled. This is not MFA registration – but if the user is in scope they will be asked to register for this as well. This therefore can result in two registrations at next login – one for SSPR and one for MFA. We will show this below, but it is best if you move to the combined MFA/SSPR registration wizard mentioned below.

SSPR Enablement

Enhanced Registration (Depreciated) – This was the new registration wizard in 2018 and have been replaced by the next option. If you still have users on this option you will see it, otherwise the option to enable this older wizard is now removed. This is accessed via > Azure AD > User Settings > Manage user features preview

MFA Registration Wizard

Combined MFA and SSPR Registration – This is the current recommended MFA registration process and it includes self-service password reset registration as well. You should aim to move your settings to this. All the new MFA reporting and insights are based on this process. This is accessed via > Azure AD > User Settings > Manage user features preview. Note that if you still have users on the previous “Enhanced Registration” shown above then this one is listed as “enhanced”. If not – if only one slider is shown – it is the new registration process. You can enable this for a group of users (for pilot) or all users:

Combined MFA and SSPR Registration Wizard

Office 365 MFA + Original Registration

This is not recommended to be used any more – use the Azure AD Free Conditional Access rules for all users or all admins instead. But for completion of the process to show all the options, you select a user(s) in the Office 365 MFA page and click Enable. In the below screenshot we can see that Cameron White is enabled for MFA. This means that it has been turned on for him, but he has not yet gone through the registration wizard:

Office 365 MFA for Single User

The video below shows the first run experience of this user – they login and are prompted to register for MFA. They register using the legacy experience and are then granted access to the application.


Office 365 MFA + Enhanced Registration

For this scenario I have a user called Brian Johnson. He has been enabled for MFA as above (Office 365 method) but additionally has been added to a group that is configured to support the new MFA+SSPR combined registration process. Brian is not enabled for SSPR. The video shows the user experience. Note that the user needs a valid licence to be able to use this experience. If they do not have any licences they will get the old experience:


Conditional Access MFA

The following video looks at the experience of two users who are enforced for MFA via Conditional Access. The login will trigger the registration for MFA as neither user is already registered. The first user (Christie) gets the old registration wizard and the second (Debra) gets the new registration wizard. The Conditional Access settings are basic – MFA in all circumstances for our two users:

Conditional Access Two Users
Conditional Access MFA Enabled

Impact of SSPR on MFA Registration and User Sign-In

When users are set up to register their password reset security methods and MFA, but using the old registration wizard the user needs to do two sets of registration. Again, it is recommended that the combined registration process is used instead of this process.

For this demostration, we are enabling SSPR for our test users. One with the old registration wizard and one with the new one:


Adding SSPR To Already Registered Users

Once a user has registered for MFA (old or new registration) it might come a time where you enable SSPR for them after that (and not at the time of original registration). In this scenario the users that registered with the old registration wizard are asked to register for SSPR, but users who went through the new wizard – though they did not specifically register for SSPR – there is enough details already available for them to use the service (as long as app notifications and codes is enabled for SSPR). If SSPR is left on the default of SMS and Email, then the new registration wizard does not have your alternative email and so SSPR is unavailable to you. The user process and flow is shown in the next video:


Azure AD Identity Protection and MFA Registration

The Azure AD Premium 2 licensed feature called Identity Protection contains the ability to request that the user registers for MFA (and SSPR if via the new combined registration wizard) even if the user is not required to perform MFA for login – all our previous registrations only required registration because the user needed to do MFA. You can ask users to pre-register via but Identity Protection adds this functionality with a 14 day option to defer. The video shows the settings and the user experience:


Azure AD Free Conditional Access for All Users

Early Q2 2019 Microsoft rolled out new baseline policies for Azure AD Conditional Access. These are available even without the Azure AD P1 licence needed for Conditional Access – but as they are licence free they are heavily restricted – they apply to all users and need MFA if sign-in is risky. So though they do not require MFA on all logins (unlike the O365 MFA legacy settings) they do require registration. But they offer a 14 day deferral process if the user is not ready to register. But unlike Azure AD Identity Protection mentioned above, you cannot do this for some users – it is enabled for all users upon enabling the rule. Lets see the settings and the user experience in the video. The video will also enable the “all admins” baseline policy as well, as that should always be turned on.

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Too Many Folders To Successfully Migrate To Exchange Online

Exchange Online has a limit of 10,000 folders within a mailbox. If you try and migrate a mailbox with more than this number of folders then it will fail – and that would be expected. But what happens if you have a mailbox with less than this number of folders and it still fails for this same reason? This is the problem, with resolution, I outline below.

I was moving some mailboxes to Exchange Online when I came across the following error in the migration batch results:

Data migrated: 18.18 MB ‎(19,060,890 bytes)‎
Migration rate: 0 B ‎(0 bytes)‎
Error: MigrationMRSPermanentException: Error: Could not create folder 2288. –> MapiExceptionFolderHierarchyChildrenCountQuotaExceeded: Unable to create folder. ‎(hr=0x80004005, ec=1253)‎ Diagnostic context: Lid: 55847 EMSMDBPOOL.EcPoolSessionDoRpc called [length=204] Lid: 43559 EMSMDBPOOL.EcPoolSessionDoRpc returned [ec=0x0][length=468][latency=1] Lid: 52176 ClientVersion: 15.20.1730.17 Lid: 50032 ServerVersion: 15.20.1730.6019 Lid: 35180 Lid: 23226 — ROP Parse Start — Lid: 27962 ROP: ropCreateFolder [28] Lid: 17082 ROP Error: 0x4E5 Lid: 25953 Lid: 21921 StoreEc: 0x4E5 Lid: 27962 ROP: ropExtendedError [250] Lid: 1494 —- Remote Context Beg —- Lid: 38698 Lid: 29818 dwParam: 0x0 Msg: f28f1e21-62aa-4999-977f-ce310efea309-61f0997f-74d5-4421-9050-64f8272e5ac2[9]-28A06 Lid: 29920 dwParam: 0xB Lid: 29828 qdwParam: 0x2711 Lid: 29832 qdwParam: 0x2710 Lid: 45884 StoreEc: 0x4E5 Lid: 29876 StoreEc: 0x4E5 Lid: 30344 StoreEc: 0x4E5 Lid: 54080 StoreEc: 0x4E5 Lid: 56384 StoreEc: 0x4E5 Lid: 38201 StoreEc: 0x4E5 Lid: 35904 Lid: 45434 Guid: f12f3e45-67aa-89012-345f-ce678efea901 Lid: 10786 dwParam: 0x0 Msg: 15.20.1730.017:VI1PR0502MB2975:145a3769-3902-4e6b-9fe4-6db564e4eb92 Lid: 1750 —- Remote Context End —- Lid: 31418 — ROP Parse Done — Lid: 22417 Lid: 30609 StoreEc: 0x4E5 Lid: 29073 Lid: 20369 StoreEc: 0x4E5 Lid: 64464 Lid: 64624 StoreEc: 0x4E5

In the above I have highlighted some of the errors I was seeing – with the “could not create folder” message, the first indicator is that I have too many folders to migrate or I have a corrupt mailbox. Running Get-MoveRequestStatistics and including a full report (with -IncludeReport) shows in part the below. This was run to get more info on the move request. This was run from Exchange Online:

​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​26/03/2019 17:10:09 [VI1PR0502MB3855] ‘MigrationService (on behalf of ‘’)’ created move request.
26/03/2019 17:10:15 [DB8PR05MB6025] The Microsoft Exchange Mailbox Replication service ‘’ (15.20.1730.17 ServerCaps:01FFFFFF, ProxyCaps:07FFFFC7FD6DFDBF5FFFFFCB07EFFF, MailboxCaps:, legacyCaps:01FFFFFF) is examining the request.
26/03/2019 17:10:15 [DB8PR05MB6025] Content from the Shard mailbox (Mailbox Guid: f12f3e45-67aa-89012-345f-ce678efea901, Database: cc980daf-4402-4645-b26c-2a83760b161c) will be merged into the target mailbox.
26/03/2019 17:10:15 [DB8PR05MB6025] Connected to target mailbox ‘\2c065e32-3bd5-4524-9aac-03880fa8e961 (Primary)’, database ‘EURPR05DG090-db014’, Mailbox server ‘’ Version 15.20 (Build 1730.0).
26/03/2019 17:10:20 [DB8PR05MB6025] Connected to source mailbox ‘\2c065e32-3bd5-4524-9aac-03880fa8e961 (Primary)’, database ‘DB’, Mailbox server ‘’ Version 15.0 (Build 847.0), proxy server ‘’ 15.0.847.40 ServerCaps:, ProxyCaps:, MailboxCaps:, legacyCaps:1FFFCB07FFFF.
26/03/2019 17:10:21 [DB8PR05MB6025] Request processing started.
26/03/2019 17:10:21 [DB8PR05MB6025] Source mailbox information:
Regular Items: 8443, 905.4 MB (949,422,345 bytes)
Regular Deleted Items: 1149, 189.9 MB (199,115,692 bytes)
FAI Items: 4651, 11.72 MB (12,285,701 bytes)
FAI Deleted Items: 9, 19.26 KB (19,721 bytes)
26/03/2019 17:10:21 [DB8PR05MB6025] Cleared sync state for request 2c065e32-3bd5-4524-9aac-03880fa8e961 due to ‘CleanupOrphanedMailbox’.
26/03/2019 17:10:21 [DB8PR05MB6025] Mailbox signature will not be preserved for mailbox ‘\f12f3e45-67aa-89012-345f-ce678efea901 (Primary)’. Outlook clients will need to restart to access the moved mailbox.
26/03/2019 17:11:20 [DB8PR05MB6025] Stage: CreatingFolderHierarchy. Percent complete: 10.
26/03/2019 17:12:38 [DB8PR05MB6025] Initializing folder hierarchy from mailbox ‘\2c065e32-3bd5-4524-9aac-03880fa8e961 (Primary)’: 29048 folders total.
26/03/2019 17:21:21 [DB8PR05MB6025] Folder creation progress: 1102 folders created in mailbox ‘\2c065e32-3bd5-4524-9aac-03880fa8e961 (Primary)’.
26/03/2019 17:31:22 [DB8PR05MB6025] Folder creation progress: 2730 folders created in mailbox ‘\2c065e32-3bd5-4524-9aac-03880fa8e961 (Primary)’.
26/03/2019 17:41:22 [DB8PR05MB6025] Folder creation progress: 4535 folders created in mailbox ‘\2c065e32-3bd5-4524-9aac-03880fa8e961 (Primary)’.
26/03/2019 17:51:23 [DB8PR05MB6025] Folder creation progress: 6257 folders created in mailbox ‘\2c065e32-3bd5-4524-9aac-03880fa8e961 (Primary)’.
26/03/2019 18:01:23 [DB8PR05MB6025] Folder creation progress: 7919 folders created in mailbox ‘\2c065e32-3bd5-4524-9aac-03880fa8e961 (Primary)’.
26/03/2019 18:11:23 [DB8PR05MB6025] Folder creation progress: 9570 folders created in mailbox ‘\2c065e32-3bd5-4524-9aac-03880fa8e961 (Primary)’.
26/03/2019 18:14:15 [DB8PR05MB6025] Fatal error StoragePermanentException has occurred

The move request logs show an increasing folder count, and when this exceeds 10,000 a storage error occurs.

So the next thing to do is to check what I have on-premises. I have generally two options to try and fix a mailbox I am moving to Exchange Online. One is to move the mailbox elsewhere on-premises (on the basis that I discard errors on-premises and then move a cleaner mailbox to the cloud) or run repairs on the mailbox. Note that running repairs on-premises is part of the move to the cloud anyway as Exchange Server does this as part of the move.

But this revealed nothing! The move request logs on-premises showed the same – there was over 10,000 folders (indeed some of my mailboxes had over 20,000 folders) and this was enumerated in the move request logs. A New-MailboxRepairRequest did nothing either. But interestingly, Get-MailboxFolderStatistics | Measure showed only 200 folders! Each of my failing mailboxes had between 150 and 263 folders – nothing like the +10,000 that the move request was finding!

So I opened the mailbox in Outlook having granted myself permissions to it – again nothing.

So I opened MFCMapi and had a look at the folders. Now MFCMapi shows everything in the mailbox, and not just items under the “top of the information store” folder. I went about expanding each subfolder I could find and I came across a subfolder that everytime i expanded it, MFCMapi would hang. I would close and restart MFCMapi and the same thing!


I had found my suspect folder – its a iPhone device that had created the +10,000 folders. Now that I had a good candidate for my issue, the fix was easy. I listed the active-sync devices using Get-MobileDevice -Mailbox “Richard Redmond” | FL Identity and then removed the suspect device using Remove-ActiveSyncDevice “ Redmond/ExchangeActiveSyncDevices/iPhone§A9BCDE7FG57HIJ81KL1M08NOPQ” -Confirm:$false where the device identity was returned in the Get-MobileDevice cmdlet run just before.

This Remove-ActiveSyncDevice (or Remove-MobileDevice) cleans up this mailbox and deletes the partnership with the device.

Once this was done, I moved the mailbox again and it was ~200 folders and moved to Exchange Online without further issue.

Where I tested the move to Exchange Server rather than Exchange Online, I found that looking in the move request report (I had prestaged the move and then removed the corrupt mobile device), the move report showed information like the following and all I had done was removed one mobile device from the mailbox!

26/03/2019 17:41:22 [servername] Folder hierarchy changes reported in source ‘Primary (a8c13a2f-535b-d996-908e-ff84b1484a7)’: 200 changed folders, 24080 deleted folders.

From the users perspective, if the phone is an active device and is syncing email, then removing the phone causes it to create a new partnership. If the server allows any device then this is seamless to the user. If the server requires authorization to add a new device, then the user will be told this and service desk/admin will need to approve the device again. So if Allow/Block/Quarantine (ABQ) is not enabled on the server, one wonders if deleting all active sync partnerships before migrating any mailbox is an idea worth considering – there could be mailboxes I have moved that are <10,000 folders but not far from that number and therefore storing up issues for the future!