After skimming through this, I navigated around this Chris Siebelmann&#x27;s site with the forward and back links, discovering something way more interesting than Unix strings and refreshingly relevant:<p>&quot;How I do per-address blocklists with Exim&quot;<p><a href="https:&#x2F;&#x2F;utcc.utoronto.ca&#x2F;~cks&#x2F;space&#x2F;blog&#x2F;sysadmin&#x2F;EximPerUserBlocklists" rel="nofollow">https:&#x2F;&#x2F;utcc.utoronto.ca&#x2F;~cks&#x2F;space&#x2F;blog&#x2F;sysadmin&#x2F;EximPerUse...</a><p>I run Exim, and I&#x27;m also a huge believer in blocking spam at the SMTP level, and also do some things globally that should perhaps be per-user. I&#x27;m eagerly interested in everything this fellow has to say.