[Mimedefang] Off Topic: Refuse Null Sender

[David F. Skoll]

Jason Bertoch wrote:

> Hi all, sorry to post off topic but searches for this only seem to return
> reasons not to attempt.  However, I have a server that is exclusively used to
> relay outbound mail.  I can't think of any legitimate reason for someone to
> relay mail from the null sender.

Some auto-responders (eg, Sendmail's "vacation") can be configured to set
the envelope sender to <>.

> Blocking this will seem to eliminate some
> back-scatter as well as botnet spam.

You should never get backscatter if someone sends as <>.  That's the whole
point of the null sender: To avoid responses, even error replies.

Regards,

David.