This has naught to do with vintage computers, but I need help, and this audience likely has one or more folks who can help. I run my own mail server; I have for many years. Lately, spamhaus.org has blocked me for ONE suspect email from my network. Here is ALL the bad activity from my IP for the last three months: (IP address, timestamp (UTC), and HELO string) 98.109.205.15 2022-03-28 10:15:00 instructure.com 98.109.205.15 2022-03-15 08:05:00 instructure.com 98.109.205.15 2022-01-21 16:10:00 localhost It's a funny kind of malware that sends two messages 15 days apart. I can't figure out where it's coming from, and my knowledge of iptables and tcpdump is insufficient to do the following jobs: 1. figure out where this bad email is coming from 2. block port 25 outbound at my firewall except from the ONE machine authorized to send email. I am willing to PAY for help with this. Email me if you think you can help and would like to try. Thanks, Bill Dudley This email is free of malware because I run Linux.