Today I had a really long discussion with our CIS about their greylisting policy. If you want to send an email to mail.tugraz.at this mailserver is checking it by doing all the rules described in:

 http://www.zid.tugraz.at/ki/internet/mail/de/filter.html

My problem was the greylisting at point 5. I am running qmail on my SMTP Server and with qmail-smtp it is out of the box not possible to check the local part aif the rcpt address. The rcpthost is checked with the equal named file in /var/qmail/control. The next problem was that my mailboxes don't have a local user, they only exist in a SQL database maintained by vpopmail.

What I have done is to write a perl plugin for qpsmtpd which checks the full rcpt address against the vpopmal and valias table in the vpopmail db. Therefore now all mails which have a rcpt which is not available on my server are rejected with a RFC conforming message! You can find the plugin on my homepage.