Qmail "from" security

[Fr3d]

Most of the spam I get now specifies to "from" field as the same address as whoever is in the "to" field.

Is there a way I can make Qmail check all incoming mail to check whether the email address that the email says it's "from" is actually supposed to come from that server? Or can I block all email from some domains if they're coming from a remote server?

I did add an SPF record for my main domain a few months ago, but it doesn't seem to make any difference :(

[Justec]

Well you need to turn on SPF blocking on your qmail which is available with the new Iworx 3.0 by editing /var/qmail/control/spfbehavior

See here for more info: http://interworx.com/forums/showthread.php?t=1117

[Fr3d]

Pity I can't upgrade :(

My entire rpm database is completely broken (along with several other things).

Thanks for the info though - I the components for my new server arriving soon, so I'll be sure to enable it on that :)