Ah excellent info. Thanks to *everybody* that replied. I understand much better now.
Most appreciated :) Mike -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Thursday, May 29, 2003 11:27 AM To: Exchange Discussions Subject: RE: The real story with Secondary MX On Thu, 29 May 2003, at 9:35am, [EMAIL PROTECTED] wrote: > Another question - how does the Secondary server KNOW that it's a > secondary server? How is it setup differently, from the primary > server? Others have answered your question well, but I feel it worth emphasizing that MX records only tell *other* mail servers what to do. They usually do not influence the actual destination servers themselves. Most SMTP implementations need to be explicitly told to handle mail for a given domain. Otherwise you get errors like "Relaying denied" or "MX loops back to me". The typical algorithm is something like this... First, the server checks an SMTP envelope's "RCPT TO" command(s). Any "RCPT TO" commands which specify a domain the server is configured to handle are accepted for processing. What exactly happens depends on the configuration, but typically, the message is either delivered locally, or relayed to a higher priority (lower numbered) MX. High availability systems may do things like use alternate routes to internal mail storage servers or things like that. Any remaining "RCPT TO" commands on the envelope are thus relay attempts. If the server is well-behaved, it will make sure the sender is authorized to relay. (This is where the "Relay denied" error mentioned above comes from.) If the relay is authorized, the server will look up the destination MX, and forward the message on to that mail exchanger. If a server discovers that *it* is the best MX, you get errors like "MX loops back to me". -- Ben Scott <[EMAIL PROTECTED]> | The opinions expressed in this message are those of the author and do | | not represent the views or policy of any other person or organization. | | All information is provided without warranty of any kind. | _________________________________________________________________ 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]
