Rodney is not a backup server in the sense that he provides mail services in the event the primary server is unavailable - he is just a backup mail exchanger. Put simply, store and forward only. While the primary server is down, the customers have no access to their e-mail; no POP, no SMTP. By using different priority levels, mail should (there are exceptions) always default to the primary. The sending SMTP should check the next priority SMTP for delivery if the primary does not respond.
One reason for having a backup mail exchanger is to control the retries yourself instead of relying on other servers to retry delivery. For example, I know of several admins who have cut down delivery retries to four hours or less (by decreasing the delay between retries and/or the number of retries). In such a case, if the primary is down for a longer period, the mail is not delivered (the sender should get a failure notice).
-Jeff
At 07:25 PM 03/13/2003 -0600, Danny Mallory wrote:
This is the obvious solution for getting the mail Rodney, and getting the mail from Rodneys server back to the primary. But some of my points are not being understood... Here is the big question.. Is Rodney really a backup server? Where do the customers pop3 their mail from while the primary is down.. As this is a DNS entry a/cname entry your either going to one or the other or your using a round robin in DNS.. But is nothing dynamic like MX records.. I assume they would always be pointing to the primary mail server to receive their mail.. Which means.. the customers get errors because the primary mail server is unavailable.. So... Why worry about it at all.. Let the smtp senders retry it until the primary guy comes back up.
Danny
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