On 16:44:19 Aug 30, Girish Venkatachalam wrote: > > I couldn't find this mentioned in RFC2821, could you point out the > > section number which talks about this? > > > > In any event, it's definitely not all that unusual... > > > > Obviously then I must be wrong. > > Mail servers are supposed to retry from the same IP address as per the > RFCs. That is what I know/think. > > Let me head to ietf.org and get back. :) >
Stuart, I got this from RFC2821. +----------------------------------------------------------------------+ 3.7 Relaying In general, the availability of Mail eXchanger records in the domain name system [22, 27] makes the use of explicit source routes in the Internet mail system unnecessary. Many historical problems with their interpretation have made their use undesirable. SMTP clients SHOULD NOT generate explicit source routes except under unusual circumstances. SMTP servers MAY decline to act as mail relays or to accept addresses that specify source routes. When route information is encountered, SMTP servers are also permitted to ignore the route information and simply send to the final destination specified as the last element in the route and SHOULD do so. There has been an invalid practice of using names that do not appear in the DNS as destination names, with the senders counting on the intermediate hosts specified in source routing to resolve any problems. If source routes are stripped, this practice will cause failures. This is one of several reasons why SMTP clients MUST NOT generate invalid source routes or depend on serial resolution of names. When source routes are not used, the process described in RFC 821 for constructing a reverse-path from the forward-path is not applicable and the reverse-path at the time of delivery will simply be the address that appeared in the MAIL command. A relay SMTP server is usually the target of a DNS MX record that designates it, rather than the final delivery system. The relay server may accept or reject the task of relaying the mail in the same way it accepts or rejects mail for a local user. If it accepts the task, it then becomes an SMTP client, establishes a transmission channel to the next SMTP server specified in the DNS (according to the rules in section 5), and sends it the mail. If it declines to relay mail to a particular address for policy reasons, a 550 response SHOULD be returned. +----------------------------------------------------------------------+ Does the last sentence of the first paragraph above suggest this? And I find several places in the RFC where this idea is strongly suggested. Going by common sense however only those who don't comply with SMTP standards would do such a silly thing. It is still possible to use a bank of MTAs but allocate the job of retrials to come from the same IP address. -Girish
