It appears that Microsoft recently made a change to Office 365 security. This change prevents any Office 365 mailbox or shared mailbox from forwarding its email to an outside system.
If your current Email2AT setup involves Microsoft Office 365 forwarding mail to Email2AT, you will need to create a new Outbound Security Policy in Microsoft Office 365 to allow these messages to flow.
You will know this is affecting you if your users are receiving bounce-backs that contain:
550 5.7.520 Access denied, Your organization does not allow external forwarding. Please contact your administrator for further assistance. AS(7555)
This issue does not affect Email2AT Advanced remote mailboxes (in which Email2AT logs into your IMAP or Office 365 mailbox to download messages).
We’ve created a very short and to-the-point video explaining the change you need to make. You can view that video here:
As always, let us know if there’s anything we can do to help!