It's called "Scatterback Spam" and it comes in waves. Your email address was probably just guessed, though it could have been harvested by anyone in the world from a BBS if that BBS has email addresses out in the open, or even just posted once.
I run my own email server for my own domain. I get, on average, 1100 spam attempts A DAY. About 800 get rejected just because my server is set to not respond to a delivery attempt for 20 seconds (instead of instantly.) About 200 get caught by the well-trained bayesian filters. Maybe 50 a day are messages from mailing lists, and they get shunted to a different mailbox. That leaves 50 messages a day, of which maybe 45 are real messages, newsletters, and advertisements from companies that I want to see. That leaves maybe 5 spams that get into my inbox.
The Scatterback Spam started about 3 weeks ago one weekend. It added about 1400 spam messages in one day, all looking like "Message Rejected" (or similar) error messages. (I never checked to see how many the 20-second delay was blocking, but I doubt it was very much, since these were legitimate servers sending error messages instead of spam-bots.) I then set up server-side filters for the most common rejection message keywords, sending them all to the spam folder on the server for later review.
The 1400 messages a day rate kept up for 3 days, then it started tapering off. After a week I was down to 100 of these a day. After 2 weeks it was about 5 a day. It has stopped after 3 weeks.
The point I'm making here is that scatterback spam can start randomly at any point, and as the spammers move on to another email address to mimic, it will die down. I doubt it had anything to do with this BBS, and neither should you.
-Llama
