We have an Exchange 5.5 server running IMAP4, LDAP NNTP and POP3 protocols along with IMS and MS Mail connectors. A different server (outside the firewall) is running the SMTP service and is routing mail to the internal mail server.
We recently installed Exchange 2003 and migrated the mailboxes and public folder off of the old 5.5 server. As long as both the 5.5 and 2003 servers are running mail transfers just fine. If the 5.5 server is down (or the IMS service is off) mail does not get routed. I've tried pointing the SMTP server outside the firewall at the new server but nothing occurs.
There isn't an SMTP connector on either the old 5.5 box or the new 2003 server. The way the e-mail is working right now is that on a web box (outside the firewall) IIS is running the SMTP virtual server and that is routing all the smtp traffic to the smart host, which is a proxy box ( 2 nics, one internal one external) the proxy box then routes all the mail to the 5.5 exchange server.
I can set up an SMTP connector on the 2003 server to point to the 2003 SMTP virtual server, but do I then need to do anything to the SMTP virtual server to make it aware that it will be receiving mail from the proxy, or just point the proxy to it and it should go? And again, at what point do I turn off the IMS on the 5.5 box?