ERS Stops sending mail to specific domains. (4313809)

The email rewriting service is not working when sending to specific domains. These domains you have added as "remote domains" within O365. Domain Rewrite is working for all other email sent externally. This can be confirmed by looking at the message tracking and seeing that email is not being routed through the ERS created connector. 

The remote domains have an "Out of Office" configuration where you can set this to "Internal" or "External". Microsoft uses this setting to determine whether or not a domain is "Outside my organization". Since the Domain Rewrite transport rules look for this specific qualifier when re-routing mail to the Domain Rewrite connector, mail no longer is caught by this rule to the specified remote domains.

Set the remote domain OOO configuration setting back to "External", which should be the default.