About that email issue [1] …
Our problems all stem from the greylist daemon [2] I wrote. Or more specifically, the interaction between the greylist daemon [3] and sendmail [4]. Or even more specifically, the greylist daemon [5] and the milter library [6].
As far as I can tell, the problem is: customer uses [DELETED-Lookout-DELETED] Outlook or [DELETED-Lookout, Exploit!-DELETED] Outlook Express, configured to use SMTP (Simple Mail Transport Protocol) AUTH [7]. Sendmail hands the authentication off to some other process, which okays it, then sendmail hands the request off to the greylist daemon, which, since it's coming from a foreign address, of course greylists it, and the customer gets an error message from [DELETED-Lookout-DELETED] Outlook or [DELETED-Lookout, Exploit!-DELETED] Outlook Express that says, “Try again later!”
And then we (or our resellers) get a call.
Sigh.
What I would like is for sendmail to skip the greylist daemon if SMTP AUTH is being used, but I'm not sure how to apply the clue-by-four to sendmail.
That's separate from the issue that spammers seem to be clueing in to greylisting and are finding ways around it …
Arg!