Erik Logtenberg a écrit : >> People who configure MX records should read the SMTP RFC, in >> particular section 5. "Address Resolution and Mail Handling. >> >> By design, Postfix enforces sane limits on ALL information. In the >> case of SMTP server IP addresses. Such limits protect Postfix >> against abusive sites. > > Thank you again for your reply, Wietse. Please forgive my relative > cluelessness regarding this issue, but could you please elaborate a bit > on what you mean? > > I just read section 5 of RFC 2821, and section 4.5.4.1 (Sending > Strategy) as well, which is referenced to in section 5. I understand > that the question of whether or not a sender should try different IP's > on a multihomed host has been controversial. > > However by pointing to this RFC you seem to imply more that the MX > records aren't configured right to begin with, at least not according to > best practice / common sense. Do I interpret you correctly? > If so, what would you consider the best way to configure MX records, > given the situation that there are 11 incoming SMTP servers required to > handle the load and they all have both an IPv4 and an IPv6 address? >
RFC 5321 (the same sentence is in 2821) says "In any case, the SMTP client SHOULD try at least two addresses." so a client that only tries two addresses is compliant. If you use twenty IPs, be prepared to see clients ignore most of them (and no tuning of _your_ postfix will help).
