I understand more now, I think. Very convoluted. If you set the machine up for an IP on ISP B, then it should work just like it did for ISP A. If it does not, I would think you have a network/ISP issue. When the machine is on ISP B, try telnetting to it on port 25 (http://wiki.qmailtoaster.com/index.php/How_to_use_telnet_for_diagnostics) See if there are any issues, and watch the logs while you do so. Also check for any firewall issues.
Quite convoluted, but like I said, we're in production; a single mail disappears and I get screamed at by everyone. When I did test the machine out, I couldn't telnet into port 25. I'm guessing it could be a firewall issue, but that's why I swapped out directly and even used the same ip address since our firewall is already configured to allow traffic in/out for that ip address. On that note, the current setups we have are direct mirrors. that's why I was wondering if there was something else going on since it works for network A but not network B. I'll try to do more testing and post here again with results. Need to wait for a testing window since our company also runs 24/7. Thanks.
