"ErrorInternalServerTransientError" error appears in Dynamics 365 mailbox

Applies to: Dynamics 365

Symptom


The following alert appears within a Dynamics 365 mailbox record:

"An unexpected error occurred while receiving email. Mailbox [Mailbox Name] didn't synchronize. The owner of the associated email server profile [Profile Name] has been notified.

Email Server Error Code: ErrorInternalServerTransientError"

Cause


This message may appear if Server-Side Synchronization attempted to retrieve emails but encountered an error. This is typically a temporary issue and the emails will be retrieved successfully on the next synchronization cycle (typically 15 minutes). 

Resolution


If this message does not persist on the next synchronization cycle (typically 15 minutes), this message can be ignored. If this message persists and email is not being retrieved by Server-Side Synchronization, you can contact Microsoft Support. There may be an issue with your email server so you can first verify you can send and receive email successfully with your email service.