Re: [exim] 451 error codes & Exchange

On 7/12/06 2:00 PM, "Dave Evans" <davide-20060629@???> wrote:

>> AFAIK 451 is a temporary error, so the MTA shouldn't drop the connection
>> (forbidden by RFC2821), but issue a QUIT and retry later.
>
> Temporary, certainly. Can anyone confirm (and preferably cite the relevant
> part of the RFC) that QUIT is the correct response, as opposed to, say RSET
> (and try the next message), or simply continuing with the remaining
> recipients? Or maybe the compliant MTA is free to choice between several
> choices of action?

At RCPT TO: time, the 451 relates to the given recipient. (For example,
that recipient might currently exceed storage quota while all others are
OK.) So the reaction should relate to the specific recipient (just as
unknown user should).

One interesting "gotcha" is that if all the RCPT TO: commands result in a
temporary error, and the sending MTA presses on with DATA even though there
are no valid recipients, then the receiving MTA is required to issue error
503 (no valid recipients). Some sending MTAs then take that as a permanent
error.

Turning off pipelining may help. See the main option
pipelining_advertise_hosts.

--John