"Domain of sender address does not exist" error

This article is for users experiencing the error:

'Domain of sender address does not exist'
or
'Domain of sender address doesn't exist'

This may happen after adding CNAME records as per Verified Senders 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 your internal DNS, or to the particular software/filter that is generating this error.

It could be that your MX server (the server that hosts your incoming email) is rejecting the email as it doesn't know about the CNAME subdomain (the one beginning with 'em') that we advise you to add.