by DrkShadow » Sat Oct 23, 2010 3:06 pm
Just a thought, it would likely be less overhead and no storage if you build an SMTP proxy. Listen for the RCPT TO line, filter it according to the database, and maybe the first few lines after DATA for bcc, cc, to: headers. Filters in real time, forwards the rest, stores nothing. If the destination server is down, the sender doesn't get to send the message; if it's not, it goes straight through; if it's rejected, the sender SMTP server gets that rejection message back and has to retry later itself, etc.
Seems like a good thing all around. Wouldn't necessarily require more work on the behalf of alternative domains (inboxfree.org), as if they use spamgourmet for the sender or use their own sendmail server, the behavior is approximately the same (difference _possibly_ being they wouldn't forward, and queue, every message through spamgourmet's SMTP server first)