I would like to tap the wealth of knowledge here for two DNS related questions. First, I had Imail setup as a secondary spooler for a company. I would see about 25,000 (1/15th of their daily total) messages pass through my server each day. Question 1: why, when their server is up and running without issues, do I see so many messages pass through me?
Most likely, it's spam. Quite a few spammers realized that lots of primary mailservers have anti-spam software, but backups do not. They hope that by sending through the backup, their spam will get through. Most anti-spam programs running on primary mailservers (like IMail v8's anti-spam) see the E-mail as coming from the backup mailserver, which is a "safe" IP, and aren't able to run any DNS-based spam tests on the E-mail.
They moved off my server this past Saturday night. However, I'm still seeing a couple thousand messages pass through my server, which I'm still forwarding for them. Question 2: why, with their TTL being 2 hours, and it being 3 days since the DNS change, do I still see messages sent to me?
Most likely, this is also due to spammers. Unless there is a good reason (for example, there old TTL was 4 days and you just changed it to 2 hours right before making the change), the spammers are keeping the information cached longer than it should be.
-Scott
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