On Friday, October 24, 2003, 11:20:19, Kris McElroy wrote: > Let me ask this then say one of my 10 MX goes down, then what is the current > effect on mail delivery?
>From RFC 2821 Simple Mail Transfer Protocol, section 5. Address Resolution and Mail Handling When the lookup succeeds, the mapping can result in a list of alternative delivery addresses rather than a single address, because of multiple MX records, multihoming, or both. To provide reliable mail transmission, the SMTP client MUST be able to try (and retry) each of the relevant addresses in this list in order, until a delivery attempt succeeds. However, there MAY also be a configurable limit on the number of alternate addresses that can be tried. In any case, the SMTP client SHOULD try at least two addresses. and a little bit later Multiple MX records contain a preference indication that MUST be used in sorting (see below). Lower numbers are more preferred than higher ones. If there are multiple destinations with the same preference and there is no clear reason to favor one (e.g., by recognition of an easily-reached address), then the sender-SMTP MUST randomize them to spread the load across multiple mail exchangers for a specific organization. So if you've got three MX's all at the same preference level the sender will randomly choose one and if it can't connect will pick another. -- [EMAIL PROTECTED] "The avalanche has already started, it is too Rod Dorman late for the pebbles to vote." � Ambassador Kosh To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/
