canned reply for people with greylisting problems:
your ISP is "greylisting".
Basically when an email arrives at your mailserver addressed to you, the FROM is checked against a whitelist for your account. If the address is whitelisted, then the email is delivered immediately.
if NOT, then the mailserver spoofs an "i'm busy, please send this to me again later when I'm not busy, how about 15 minutes from now", and you do NOT get the mail.
If within 15 minutes the SMTP mailserver that generated the mail sends it again, the address is added to the whitelist and you get the mail. This means the first time someone emails you it will take 15-20 minutes for you to receive their email, but the rest after that will be fast as usual.
Spambots are rarely "RFC-compliant" to do with delay responses. They can't use their host ISP's SMTP server to relay mail because they'll be quickly identified and the account blocked by the ISP, so they run their own internal SMTP system on the infected computer. They have millions of other people to spam, and don't have time to pay attention to delay messages, and as such never queue and resend the spam. (they are "not RFC compliant") So greylisting is very effective against spammers.
You appear to be receiving regular emails from an "RFC Ignorant" mailing system that is direct mailing instead of relaying through their local SMTP server. (or their local SMTP is ignorant) Either way, technically the problem is on their end. But practically, you may just need to find a way to access your whitelist and add them to shut it all up.
OOOOKAY now for your personalized response now that you have the background on greylisting:
A spamzombie has YOUR email address in its database. When it blasts its spam, it randomly picks one of the many in its list to put into the "FROM" field of the spam it sends to everyone. Sometimes it's YOUR address. So when it spams to a greylisting server, it bounces the "try later" back to the sender, in the FROM field... to you.
There is very little you can do about this. Sorry. You're collateral damage in the war on spam. Consider yourself lucky. This zombie apparently is picking randomly so you're only getting hit a little bit. SOME zombies pick a specific sucker in their list to put in ALL the from's for an entire batch they send. This can easily result in thousands of what they refer to as "backscatter spam" getting sent to a single person's address from a bunch of greylisting servers. Again, there's really nothing you can do about that short of put a rule filter on your inbox to trash it on sight. Be grateful it's easy to Rule on because it's consistent, unlike the spam itself that tries very hard to be difficult to filter.
