Ok. I run my own email server (using Qmail - its awesome) but have recently discovered that I occasionally get spammed by some annoying locations, such as mrktmail.com. I figure - hey, lets block them at the iptables firewall level, so they can't connect via smtp.
I check the header of one of the spam mails and discover that they are on the 18.104.22.168 subnet. So I block that subnet in iptables.
I do an iptables -l and among the rules is:
DROP all -- 22.214.171.124/24 anywhere
So far so good.
But I'm STILL getting the spam mail.
What am I doing wrong here? ???