[TriLUG] OT: ATT UVerse internet access

[bak]

On 3/31/11 2:23 PM, Chris Merrill wrote:
> On 3/30/2011 3:29 PM, bak wrote:
>> I got around this by using the 'submission' port. Modern UNIX MTAs have
>> this turned on by default. It is basically just
>> SMTP-with-authentication-by-default; no relaying. The well-known port is
>> 587. See RFC2476.
> 
> I was not aware of this port.  But I'm a little confused about the "no relaying"
> part.  If I am using it to send email to our customers, is that not relaying?
> If not, then I don't understand the distinction. I thought contacting an SMTP
> server to send e-mail to a user on some other server IS relaying ???

I think my brain was looking at it from a server rather than a user
perspective when I wrote that.

An MTA's regular SMTP port will do two things:

-- Allow anyone[1] to relay a message into it, unauthenticated, as long
as it understands that it is responsible for mail for that domain/address

-- Allow an authorized group of people, after being authenticated, to
submit a message that will be forwarded to any address

The submission port is meant do the second thing, but not the first.

Sorry to be imprecise :)

[1] Usually after being subjected to various anti-spam measures like a
blackhole list, header checks, reverse name lookup, size limitations...


--bak

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