550 5.1.8 Access denied, bad outbound sender AS(42003)

“Your message couldn’t be delivered because you weren’t recognized as a valid sender. The most common reason for this is that your email address is suspected of sending spam and it’s no longer allowed to send email. Contact your email admin for assistance.” This is an error you get when your anti-spam “outbound” policy restricts… Continue reading 550 5.1.8 Access denied, bad outbound sender AS(42003)

[New] External Email Notification in Exchange Online

This is a new feature released in March 2021 that adds support in Outlook (Mac, OWA, Mobile) for the display of the external status of the sender – note at the time of writing it does not add this feature to Outlook for the PC. This should be used to replace the way this has… Continue reading [New] External Email Notification in Exchange Online

Exchange Online Warning On Receipt Of New Email Sender

First Contact Safety Tip

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… Continue reading Exchange Online Warning On Receipt Of New Email Sender

Enable EOP Enhanced Filtering for Mimecast Users

Email

Blog post updated March 2020 to include more specific IP ranges for all Mimecast regions and to fix an issue where the email sender is also using the same Mimecast region as yourself and the risk of SPF failures. Enhanced Filtering is a feature of Exchange Online Protection (EOP) that allows EOP to skip back… Continue reading Enable EOP Enhanced Filtering for Mimecast Users

Anonymous Emails Between On-Premises and Exchange Online

When you set up Exchange Hybrid, it should configure your Exchange organizations (both on-premises and cloud) to support the fact that an email from a person in one of the organizations should appear as internal to a recipient in the other organization. In Outlook that means you will see “Display Name” at the top of… Continue reading Anonymous Emails Between On-Premises and Exchange Online

Enable Report Message Add-In For Office 365

There is a new add-in available for Outlook and OWA in Office 365 that can simplify spam and phishing reporting to Microsoft for content in your mailbox. I recommend rolling this add-in out to everyone in your Office 365 tenant and for Office 365 consultants to add this as part of the default steps in… Continue reading Enable Report Message Add-In For Office 365

Get-SpoofMailReport in EOP

Using Office 365 or EOP to protect your email and worried about spoofed emails? Then try this cmdlet in Remote PowerShell for EOP: PS C:\Users\brian.reid> Get-SpoofMailReport Date                Event Type Direction Domain Action       Spoofed Sender              True Sender     Sender IP—-                ———- ——— —— ——       ————–              ———–     ———14/04/2016 00:00:00 SpoofMail  Inbound          GoodMail     no-reply@domain.com         mandrillapp.com 198.2.186.0/2418/04/2016 00:00:00 SpoofMail  Inbound         … Continue reading Get-SpoofMailReport in EOP

Is Your SenderID/SPF or DKIM Record Correctly Configured

With Microsoft having just announced that DKIM is coming to Office 365 soon (release notes here) and SenderID is already available, I thought this is a good time to write a blog on the use of DMARC to show if your records are correct. DMARC is a protocol that allows you to see the effect… Continue reading Is Your SenderID/SPF or DKIM Record Correctly Configured

Cannot Send Emails To Office 365 or Exchange Online Protection Using TLS

I have found this is a common issue. You set up an Exchange Online Hybrid or Exchange Online Protection (EOP) stand alone service and follow all the instructions for the creating of the connectors needed, only to find that your emails queue in your Exchange Server. If you turn on protocol logging you get this… Continue reading Cannot Send Emails To Office 365 or Exchange Online Protection Using TLS

Moving Exchange Online Protection Junk Mail to the Junk Email Folder

If you use Exchange Online Protection (EOP) to filter your email in the cloud and to remove spam and malware before onward delivery to you, and if you use Exchange 2007 or later on-premises, then you need to configure Exchange to move detected spam to the Junk Email folder in Outlook. By default EOP detects… Continue reading Moving Exchange Online Protection Junk Mail to the Junk Email Folder