Inbound emails were delivering normally then stop unexpectedly.
This often occurs after a discovered address expires without any action having been taken by the admin. If the email address is in fact desired to be able to send and receive email, it should be removed from the Marked Invalid List.
Find if email is on the Marked Invalid List and Removing it from that List
Description or other notes about this first multi-step task
- Navigate to Users & Groups > SMTP Discovery.
- From the dropdown, select Marked as Invalid List.
- Find the email on the list and check the box beside it.
- From the Select dropdown, select Remove from Invalid List.
- Click Apply.
Remember you need to create the user after doing this. Removing from the invalid list will not create the user automatically. There are 30 to 40 minutes of Propagation time after creating a new user.
Invalid email addresses are summarized in our SMTP Discovery reports, which are run weekly.
See: SMTP Discovery for more information on SMTP Discovery reports
To minimize administration requirements and to ensure an accurate email list for future reference, please consider using Active Directory Sync or Azure Active Directory Sync.