The Swamp!

In qmail, you can blacklist spammers and other senders (ie: an accidentally messed up machine) by blocking their server via ip and/or server name.

Here's how you edit the relevant file to do that:

# ADMINING BLACKLISTS WITH A QMAIL-ACCESS FILE:

Q: How do i "activate" the /etc/tcp.smtp file, and which address in it do i need to change?
Note: You may see many email addresses in the tcp.smtp file .

A: If you have qmailctl working on your specific qmail installation, run:
qmailctl cdb  

# You can also try this:
tcprules /etc/tcp.smtp.cdb /etc/tcp.smtp.tmp < /etc/tcp.smtp


more digital solutions found at:
xdose.com
ContentAndAds.com
qmailrocks.org
FreeBSDRocks.net
GoodCleanEmail.com
TheSwamp.info
FileCorner.com