> -----Message d'origine----- > De : Leonardo Fogel [mailto:[EMAIL PROTECTED] > Envoyé : jeudi 1 septembre 2005 23:50 > À : [email protected] > Objet : [xmail] Re: messages to yahoo and or hotmail does not get > delivered > > > > 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. >
Don't know exactly statements in RFC but John (Kielkopf) find a detail in RFC 2821 Section 5 So I suppose (I'm not a smtp rfc specialist and didn't read all ..) : A MTA must try all mx's until success and NEVER try any A domain record if one or more MX entry exist. Then if the mta get a mx record resolution returning multiple ips, the mta must try all the ip's until success. Then, depending of the mta number of 'retries' configured, the mta redo the loop again (all mxs , and for each mx entry, all ip's for this mx) Then, if none success, return a NDR (No delivery report) to the sender So with hotmail.com and hotmail (4 mx entries, and each mx pointing to 4 ip's), and assuming the MTA is configured to try 4 times to deliver (normal first attempt + 3 retries), a final NDR can only be send after 64 physical connections ( 4 mx * 4 ip * 4 attempts or total number of ip's * number of attempts). Francis - 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]
