4 messages in net.sourceforge.lists.courier-usersRe: [courier-users] Found small bug i...
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Matthias WimmerNov 27, 2007 6:14 pm 
Sam VarshavchikNov 27, 2007 6:48 pm 
Arturo 'Buanzo' BusleimanNov 28, 2007 2:33 am 
Matthias WimmerNov 28, 2007 3:02 am 
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Subject:Re: [courier-users] Found small bug in rfc1035/rfc1035mxlist.cActions...
From:Matthias Wimmer (m@tthias.eu)
Date:Nov 28, 2007 3:02:37 am
List:net.sourceforge.lists.courier-users

Sam Varshavchik schrieb:

You will find that DNS servers will themselves randomize the order of IP address and MX records of the same priority, so the order of records that have the same priority is completely irrelevant here.

Yes, I know that and therefore your code is perfectly okay as long as a mail server only uses IPv4 connections. But the order the server should process IPv6 and IPv4 addresses is NOT random.

See RFC 3974, section 3, point 5, the note there:

NOTE: If one or more address records are found, an implementation may sort addresses based on the implementation's preference of A or AAAA records. To encourage the transition from IPv4 SMTP to IPv6 SMTP, AAAA records should take precedence. The sorting may only reorder addresses from MX records of the same preference. RFC 2821 section 5 paragraph 4 suggests randomization of destination addresses. Randomization should only happen among A records, and among AAAA records (do not mix A and AAAA records).

Matthias

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