I think most web browsers will cycle through A records until it finds one that works. I see no reason why an MTA shouldn't.
RFC 2821 Section 5 says: "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." To me, this implies that Xmail should be trying the alternate A records. I do know that if any MX records exist for a domain, you should never fall back to the A record for that domain -- even if you're unable to connect to them. Does Xmail obey this? Leonardo Fogel wrote: >Although yahoo.com has 4 mx records and each mx record >has 4 A records: > > yahoo.com. ... MX 1 mx1.mail.yahoo.com. > yahoo.com. ... MX 5 mx4.mail.yahoo.com. > ... > mx1.mail.yahoo.com. ... A 67.28.113.10 > mx1.mail.yahoo.com. ... A 67.28.113.11 > ... > mx4.mail.yahoo.com. ... A 66.218.86.156 > >xmail tries only one A record for each mx record, in >case of successive failures. This is by design. > >Please, is it an RFC recommendation? I understand the >multiple A records are intended to provide load >balance, but what is an mta supposed to do in case of >failure? Shouldn't it try all A records till success? > >Many thanks. > >__________________________________________________ >Converse com seus amigos em tempo real com o Yahoo! Messenger >http://br.download.yahoo.com/messenger/ >- >To unsubscribe from this list: send the line "unsubscribe xmail" in >the body of a message to [EMAIL PROTECTED] >For general help: send the line "help" in the body of a message to >[EMAIL PROTECTED] > > > > - To unsubscribe from this list: send the line "unsubscribe xmail" in the body of a message to [EMAIL PROTECTED] For general help: send the line "help" in the body of a message to [EMAIL PROTECTED]
