Re: retry question
2008-08-06 15:03:34
Hi Hector,
At 03:27 AM 8/6/2008, Hector Santos wrote:
Explain why (Falls Under SUBMIT) and why it could not use the same,
similar or simpler retry strategy?
The roles have been split into MSA and MTA. The MUA talks to a MSA
(submission agent). The MSA requires authentication and fixes
headers whereas the MTA only acts as a relay or passes the message to
a LDA for delivery.
The MUA doesn't require a retry strategy as it falls within the same
administrative domain as the MSA. MTA to MTA communication can be
across different administrative domains. In a nutshell, if there is
a misbehaving MUA, you can do something about it whereas you may have
no control over the remote SMTP server the message is being sent to.
SUBMIT requires authentication which is not a required setup for MUA
software. The server dictates this. Not the MUA. So outside of
authentication, from the POV of the server, it wouldn't know the
difference and the MUA's MTA component is expected to behave just
like any other MTA.
As i said above, the roles are different and MSA may perform some
functions that MTA do not do.
Of course, the MUA are not generally considered mailing list
material but I have a few customers who use their MUA for the
purposes of sending large CC/TO list. Don't ask why, I've been
trying to convince them to use the list server they already have but
don't use. :-)
The MUA doesn't send the messages to the MX host for these
receivers. MUAs can also provide feedback to the end-user whereas
MTAs do not provide the kind of feedback which requires human
intervention, i.e. fixing an invalid email address.
Agreed, but there is no reason a MUA designer could not automate it
just like a normal backend automated MTA. I see no reason why a MUA
could not offer these options or something simple like them:
Direct-to-MX is frowned upon nowadays.
[X] Continue trying for __X_ attempts
Retry every X hours|Minutes
[X] Queue 4xx Failures
[X] Remove, but do not stop transactions with 5xx RCPT rejections
and still make it so its "Friendly" for users.
Right?
You can do that above in a MUA. However, if your MUA is returning a
4yz, then it generally means that something is wrong as MUAs
generally see 2yz and 5yz codes.
Its not unreasonable, there were technologies originally designed
for end users, eventually been automated for networking. In fact, I
will suggest many online hosting systems started as interactive user
online access/point systems, and then someone added a mail point
transport or frontend to it :-)
The landscape has changed since then. I doubt you would be able to
do the above in today's mail environment.
Regards,
-sm
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