Bounced Email and Null Senders

Just got a note from my host after a client said mail was bouncing to her. Turns out that my host uses some spam-prevention techniques that will bounce email that doesn’t comply. In my opinion, this sounds like an issue that the sending party’s host should deal with as our host is just battling spam.

It appears that the sender mail server does not support the callbacks the our mail server is performing. When a message is sent to our servers, our mail service will call back to ensure the sender exists. During this, the mail service uses a null sender. It appears that the sending mailserver does not support this null server and so the call back fails.

All of our servers perform the sender verification callback. This is a feature that reduces a large amount of spam from falsified e-mail addresses. We cannot turn this feature off due to a mail server not conforming to RFC standards.