[dmarc-discuss] MLM and Header-From rewritting - the SMTPopen-relay analogy

Matt Simerson matt at tnpi.net
Sun Jun 8 10:18:52 PDT 2014

On Jun 8, 2014, at 8:50 AM, Al Iverson via dmarc-discuss <dmarc-discuss at dmarc.org> wrote:

> On Sun, Jun 8, 2014 at 12:13 AM, Dave Crocker <dhc at dcrocker.net> wrote:
>> Again, closing relays carried an entirely adequate alternative via port
>> 587 for authorized users.  No such equivalence is available when DMARC
>> breaks mailing list use.
> Not at first it didn't -- it looks like port 587 submission was
> specified in RFC 2476 which was December 1998. The relay wars were
> underway by then and it took some time to garner acceptance and
> adoption.

Correct, at first SMTP submission didn't exist, but POP before SMTP sprang up almost overnight. POP before SMTP essentially "solved" the open relay problem for most sites.

I don't recall SMTP submission taking any time at all to gain acceptance. Most ISPs implemented port 587 as soon as we heard about the idea at (probably) ISPCON/BBSCON, and well before it was standardized.  The reason submission took so long time to gain *adoption* was for two reasons that immediately come to mind:

	1. POP before SMTP existed and was *really* easy for the ISP to set up
	2. SMTP submission required end users to change their mail settings.

The long tail of conversion to submission frequently looked like, "wait until the customer has a problem and then update their settings."  For some, the problem came along quickly, in the form of ISPs blocking outbound port 25 and the PBL. But that conversion is still ongoing, as some there are *still* ISPs with clients that rely on POP before SMTP.  Those sites also offer port 587.


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