We use LOCAL (blackholes.five-ten-sg.com) and SBL zen.spamhaus.org) blocking lists. You will not receive email from any machine on those lists. Note that these all block by the IP address of the sending mail server. You can also select your own custom list of DNS based lists, by either recipient address or recipient mail domain.
We use the DCC to block bulk email - and this applies to both incoming and outgoing messages. If you sign up for any mailing list subscriptions, we need to know those addresses so we can whitelist them on the incoming side. If you attempt to send any single message to more than 20 recipients, it will be rejected. Bulk outgoing mail (more than 20 recpients) needs to be arranged in advance. Consider the use of a majordomo mailing list to handle such outgoing mail.
Procmail filtering - your procmail filter can send anything to the bit bucket in the sky.
Virus scanning - all attachments are scanned using Amavisd-new.
POP3 / IMAP4 / HTTPS access to the mailbox (unless you are forwarding to another mailbox).