"Domain of sender address does not exist" error
This article is for users experiencing the error:
'Domain of sender address does not exist'
'Domain of sender address doesn't exist'
This may happen after adding CNAME records as per Sender Domain setup.
The CNAME points to a subdomain on your DNS and, generally, this requires no extra action on your part. However, if you are experiencing the above error, the solution is to add the subdomain used in the CNAME record (it begins with 'em') to the your internal DNS.