Well, I've only used this setup in the *nix world. However, this is how it tends to work.
The sending SMTP server does an MX lookup on the e-mail destination domain, and grabs the address of the lowest numbered MX. It attempts to make an SMTP connection to that server. If it fails, it will then do another MX lookup, this time grabbing the next lowest numbered MX. Some mail servers will grab all MX records during the first lookup. Some mail servers will also attempt to use the secondary MX if it encounters an error during the SMTP session with the primary MX. I have no idea what Exchange would do in this case. When the secondary MX receives a message, it will automatically attempt to forward it to the primary MX (determined via DNS), unless told to do otherwise (usually via manual routes). The secondary MX will keep trying to contact the primary MX for a set amount of time. If it times out, it should return an NDR to the sending SMTP server. Steven --- Steven Dickenson <[EMAIL PROTECTED]> Network Administrator The Key School, Annapolis Maryland -----Original Message----- From: Mike Anderson [mailto:[EMAIL PROTECTED] Sent: Thursday, May 29, 2003 10:22 AM To: Exchange Discussions Subject: The real story with Secondary MX Hello, This is still a mystery to me. Could somebody explain, or point me in the right direction, as to how this all REALLY works? And also, to make sure things are configured correctly (on the secondary server)? What is the overall process, on how mail gets routed - and the criteria that has to be met, before a Primary mail server is given up on, and then gets sent to the secondary server? Obviously, it all begins with DNS - you have preferences using numbers. The lower the number, the higher the priority the Mail Server is. So, the first MX gets a setting like '10', and the secondary MX gets a setting like '20'. Once that is done - what really happens, if in fact, the primary server is unreachable? Does the secondary Mail Server actually need to have all the User Accounts and Domains that the first server has in order to accept messages? OR, does it accept literally everything, and then spools the mail, once the Primary Mail Server is reachable again. And that leads me to the next question - how does the secondary Server know that it just accepted mails (temporarily) for a primary server, and that it's supposed to periodically contact the Primary - so it can offload all the mail it's been accumulating this whole time? If somebody could explain the whole process, or refer me to an article of some type, I would be very grateful. Thanks in advance, Mike _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Web Interface: http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&text_mode=&lang =english To unsubscribe: mailto:[EMAIL PROTECTED] Exchange List admin: [EMAIL PROTECTED] _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Web Interface: http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&text_mode=&lang=english To unsubscribe: mailto:[EMAIL PROTECTED] Exchange List admin: [EMAIL PROTECTED]
