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I have looked up

Exchange 2010 Support for RFC Standards

but do not see RFC 3848 amongst the supported standards. I do see RFC 4954 listed, which 'recommends use of RFC 3848 transmission types', though I cannot tell if this means any mail server compliant with 4954 must also be compliant with 3848.

Specifically, I am trying to find out whether Exchange is capable of adding 'ESMTPA' or 'ESMTPSA' extensions to email headers to indicate SMTP authentication. It would seem peculiar if Exchange did not support this standard...

Thank you.

Winterpool
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  • Has [this](http://arstechnica.com/civis/viewtopic.php?f=17&t=1264731) helped in any way? :-) – ckujau Feb 05 '15 at 08:47

1 Answers1

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RFC 3848 transmission types included commands such as EHLO and a few others that you might see today. ESMTPA introduced EHLO as a command that it was an SMTP server that could handle additional commands compared to standard SMTP, this command is now required per RFC 5321.

The ESMTP format was restated in RFC 2821 (superseding RFC 821) and updated to the latest definition in RFC 5321 in 2008. Support for the EHLO command in servers became mandatory. Exchange does support part of the RFC that you referenced at the beginning, but apparently not all of it.

I would check to see how Exchange supports RFC 4954. That would answer your SMTP AUTH question more in-depth.

Steve Dolinsky
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