[Cryptography] SUBMIT is not SMTP, was IAB Statement on Internet Confidentiality

Jerry Leichter leichter at lrw.com
Wed Nov 19 15:00:57 EST 2014

On Nov 18, 2014, at 11:54 PM, John Levine <johnl at iecc.com> wrote:
>> Um, not SMTP? Then what protocol does the MUA use for submission?
> It uses SUBMIT, which is similar but not identical to SMTP.  See RFC
> 6409 which updates RFC 4409, published in 2006.  That was eight years
> ago, and it's a little dismaying to find people that far out of date
> pontificating about how mail works.
To be a bit less doctrinaire about this:  "SMTP" is the name used by pretty much every piece of user-facing software in existence today.  The host you send mail to is pretty much universally "smtp.example.com".  Every server response string I've ever seen says "SMTP" or "ESMTP".

MacOS lets you configure the port to use for your "SMTP" server, but in general you accept its default ports - 25, 465, 587.  (I think during verification it tries them in order, and accepts the first one that lets it log in to the designated server.)  iOS doesn't have any explicit text of this sort, but it appears to do the same thing.

I don't have a recent Windows box around to check what how it describes things, and my Android phone is at home.

So, sure, within the community of email experts, the protocol may have a new name, and port 25 may be effectively deprecated.  It's perfectly legitimate that experts in the domain speak in those terms.  But to everyone else in the world, it's still "SMTP", and 25 remains a possible submission port (even if it's blocked on most networks), and if an expert wants to communicate with everyone else ... he needs to be aware of that.

                                                        -- Jerry

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