We swapped out a low budget firewall and installed a new SonicWall today and mail does not seem to be flowing. As fate would have it, our ISP accidentally changed our MX yesterday so I understand why inbound mail doesn't reach us yet. However, I can not send mail outbound either.
From the Exchange 2000 server I can telnet at port 25 to a remote Exchange server ad get SMTP prompt. Likewise, RDP to the remote server, I can telnet back to our internal Exchange and get SMTP. If I look in the queues on Exchange, all mail is getting dumped to the "Messages with unreachable destination" queue. I enabled SMTP logging and enabled diagnostic logging on SMTP, but can't seem to get any more info.
Any suggestions for things to try. Would DNS present a problem for outbound mail? I do have SonicWall IPS and email filtering, but they don't show anything SMTP related in the logs.
Thanks for anything,