If any messages you are sending through us result in a bounce messages that reads as follows:
From header sender domain not verified (DOMAIN.COM)
On your Sending > Verified Senders page
verify the sender domain or email to be allowed to send.
This means you are not hosting your DNS with us.
You need to go to your DNS provider and add the following two CNAME records so that your messages get through:
em460536.DOMAIN.COM
s2g-return.niner.nets460536.domainkey.DOMAIN.COM
s2g-dkim.niner.net
Of course, DOMAIN.COM must be your actual domain.
If you rely on forwarding any messages to another domain, your senders will likely get the same bounce message. The solution is to stop the forwarding.
Please let us know when you have added the two new records, and we will complete the process.