In the last seven days, SpamAssassin has placed 2975 messages in my personal spam folder. There was a definite upsurge in spam volume starting in October. As such, I've added additional filters to my mail server. Here are yesterday's stats:

First, I block anyone coming to me from an IP on a wide variety of black lists:

   2027 Client host rejected: On DNSBL cbl.abuseat.org
     72 Client host rejected: On DNSBL list.dsbl.org
     38 Client host rejected: On DNSBL dnsbl.njabl.org
     15 Client host rejected: On DNSBL sbl.spamhaus.org
    541 Client host rejected: On DNSBL dnsbl.sorbs.net
      2 Client host rejected: On DNSBL multihop.dsbl.org
      3 Client host rejected: On DNSBL dnsbl.antispam.or.id
      0 Client host rejected: On DNSBL relays.ordb.org
      0 Client host rejected: On RHSBL rhsbl.antispam.or.id
      3 Client host rejected: On RHSBL ex.dnsbl.org

Previously the messages above would've been refused 'cause most of them are to addresses that don't exist on my system. Still, some get through:

    611 Recipient address rejected: Access denied

Do that three times and you get a 24 hour ban:

    399 Client host rejected: bounce

And I block anyone who has sent me spam in the last 24 hours:

     51 Client host rejected: spam

I've started blocking any message who's sender address's domain doesn't resolve:

    153 Sender address rejected: Domain not found

One attempt to relay through me... these probes are very rare now, showing just how rare open relays actually are now.

      1 Relay access denied

This one requires the most explanation, though I think it's had a real impact on my spam volume and server load. One of my users has all of his mail forwarded to a Yahoo mail account. Yahoo does something clever, sender address based bounce throttling. If a sender address has too many bounces then they start defering the messages. They'll let them through eventually, but that'll only happen if they aren't talking directly to a spammer (spammers don't defer and retry). So I look for these warnings in my logs, purge the queue entries if they're still active and add them to one of my 24 hour black lists. I'm gonna start doing what Yahoo does soon, myself. (The lists are pretty small, considering the number of blocks. I currently have 4 IPs listed and 22 email addresses. All of these blocks came from the email address blocking.)

    209 Sender address rejected: Yahoo

Of the messages that made it through the above filters, I run some of them through SpamAssassin:

    107 Identified as Ham
    472 Identified as Spam

The rest are being forwarded to remote systems, which hopefully have spam filtering of their own:

    836 Unfiltered