List Mail User wrote: > tuxorama.com does a SMTP probe for every posting to this list > and is one of the very few IPs I have firewalled off. The probes seem > to always come from 81.169.185.26 (now they'll probably change IPs and I'll > have to block some other IP or range), so they, while irritating are very > easy to block. Asking them to stop seems to result in them stopping for > a week or so, then beginning again. They likely have one or more users > who subscribe to this list.
It's almost certainly someone who uses milter-sender. milter-sender does this dummy check before accepting mail. It's taking the "verify MX record of envelope sender" one step further and verifying the whole address. I personally find them rather inoffensive, but then again, I don't find many things offensive that some of the right-wing admins go ballistic over.