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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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