How do you configure sendmail to reject Email with a Date header too far from real time?

Question

A friend of mine using (I believe) qmail has it configured to reject, as SPAM, any incoming Email with a Date: header that is too far from real time. I can't figure out how to do this with sendmail. How do you do this?

Answer 1

Sendmail is evil ;) One solution could be to install SpamAssassin and integrate it with spamass-milter into your mail services. This has the advantage that you could activate lot of other Anti-Spam rules. Or just write your own plugins which is really easy.

Answer 2

Sendmail isn't good at filtering messages on its own.

In theory it wouldn't take much to write a simple milter (sendmail mail filter) plugin to do just that job.

However if spam prevention is the primary requirement, then why not go the whole hog and plugin a full anti-spam system?

Answer 3

Consider integrating something like MailScanner which can utilize SpamAssassin, ClamAV, and other external tools for detecting spam, viruses, and other nasties.

Also, you probably only want to use a date too far in the future or past as part of a spam score rather than rejecting it outright. You risk catching legitimate senders with misconfigured systems or mail clients in this way.