Each time an incoming message arrives at our server one of two actions occur:

• The message is rejected, and returned to the sender.
• The message is accepted, and delivered on to you.

In the first case, when a message is rejected, an error is generated by our server. This ultimately results in a bounce-message - ie. The sender of the message receives some kind of error indicating that the delivery of their message failed.

We have many different types of error messages which are caused by different tests applied against incoming mail, but as of today the bounce messages have become a lot friendlier.

Here is an example of our improved rejection notices:

This is an automatically generated Delivery Status Notification

Delivery to the following recipient failed permanently:

    test@test.org

Technical details of permanent failure:
PERM_FAILURE: SMTP Error (state 16): 552 not a valid user: test
See http://mail-scanning.com/reject/for details.
ID: MSG-678956

Two parts of this message are new:

1. There is a link to our website explaining the rejection.
2. The ID for the specific message is included.

By listing the message ID in the bounce message we allow senders who feel their message was rejected unfairly to get in touch and ensure their message is resent - and to avoid rejecting them in the future.

In the future it might be possible for a user to merely click upon a simple link to redeliver their messages, however that is open to abuse.