[ On Tuesday, October 10, 2000 at 20:34:46 (+0100), Philip Hazel wrote: ]
> Subject: Re: [Exim] Failing behviour based on SMTP codes.
>
> Oh, wait. Are you saying you get a 550 upon connection? Or in response
> to the EHLO command? In those cases, yes, Exim treats it as a problem
> with the host, and will try the message again later. Maybe it shouldn't.
> Maybe that should be configurable, but at present it isn't.
Strictly speaking a 5xx error is a permanent error no matter where in
the conversation it occurs. RFC-821 Appendix E strongly suggests a
bounce is the only sensible action, even if the error can be corrected,
since only the sender will know how best to handle the message.
Any host that answers a HELO/EHLO with a 5xx and then expects to get the
message at a later time is broken. Any MX host that answers HELO/EHLO
5xx and expects another MX to accept the message is also broken.
The only exception is perhaps EHLO which might conceivable merit a retry
with a HELO command, especially if the answer is actually 503, though as
we've seen in another recent thread even that case can be confusing when
a mailer has explicitly advertised that it is expecting EHLO.
The worst possible thing a mailer could do would be to leave the errant
message in limbo where the sender has no clue about its disposition. I
would suggest that if Exim is to freeze messages when an error occurs
during the SMTP greeting that it also immediately send a delivery status
reply to the sender....
--
Greg A. Woods
+1 416 218-0098 VE3TCP <gwoods@???> <robohack!woods>
Planix, Inc. <woods@???>; Secrets of the Weird <woods@???>
