On Thu, 31 May 2007, John C Klensin wrote:
I believe that, with the way the text in 2821 is written, a
client that is successful in opening an SMTP session (getting
the 220 greeting, sending an EHLO command, and getting a
response) to at least one of smtp1 or smtp2 is not permitted to
fall back to backup.foo.example under any circumstances.
No: it says "the SMTP client MUST be able to try each of the relevant
addresses in this list in order, until a delivery attempt succeeds", so
after a successfully established connection but a failed (4yz) delivery
the client will try another server.
f.a.n.finch <dot(_at_)dotat(_dot_)at> http://dotat.at/
DOGGER: EAST OR NORTHEAST 3 OR 4. SLIGHT OR MODERATE. SHOWERS, FOG PATCHES.
MODERATE OR GOOD, OCCASIONALLY VERY POOR.