Hello,

We have an account that have their primary MX set to an external server, and then a lower priority MX set to our server.

The default email address for the account is set to :fail:

The following happens:

telnet ourserver.com 25
helo
250
mail from:nonexistingaddress@domain.com
250
rcpt to:nonexistingaddress@domain.com
250 Accepted


The email address doesn't exist, but because we are not the primary it appears that the :fail: is not considered.

So it looks like exim accepts the email, and then attempts to deliver it to the primary MX.

The primary MX has a block for our IP (presumably because we have been allowing spam to relay to it) and so our server cannot forward the email. So it creates an undeliverable message to nonexistingaddress@domain.com - again which needs to go to the primary MX which has us blocked.

This email then sits in the queue until it times out. There are hundreds of these and the email queue reaches 2000 and alerts.

Is this behaviour right? Is there something we can do to stop this?