Re: Fwd: Balsa default mail submission on TCP port 587, not port 25[major@satx.rr.com]

[<balsa microwave com>]

Ok, perhaps not a 'port' field, but some indication of what a defaut value
is. Perhaps if someone enters just "smtp.foobar.com", it should
automatically add (not just internally, but in the displayed setting as
well), the :587 (or whatever the official designator is)..

I can think of no other MUA that both defaults to what is (irt current
deployment) a non-standard port, and ALSO gives no immediate indication
that it has done so..


On Mon, 9 Jul 2001, Brian Stafford wrote:

> On Mon,  9 July 16:17 balsa@microwave.com wrote:
> >
> > Perhaps, as was suggested, this should be made more apparent by adding a
> > "Port" field to the relevant dialog, which shows the default if it is not
> > changed.
>
> The reason this is not the case can be found in the archive.
>
> In summary, as features are added to libESMTP the syntax of the host:service
> field may be expanded to allow for the greater flexibility, e.g. URI syntax
> may be more appropriate in the future.  Now that libESMTP uses the protocol
> independent getaddrinfo() resolver interface, specifying port numbers at
> all may be considered to be wrong.  The remote host should be specified
> as a domain name and a service name.  Taking these two considerations
> together it is obvious that forcing the application to guess the correct
> syntax from two fields is fraught with difficulty.
>
> Furthermore, mail submission is fundamentally a different protocol to
> SMTP.  Just because it looks the same on the wire does not mean it has the
> same semantics.  Different things can happen when connected to an MSA on
> 587 than to an MTA on 25.  See RFC 2476 for examples of the differences.
> Although it looks like a duck and quacks like a duck, it certainly is not
> a duck.
>
> Users must be aware that submitting mail on port 25 may not behave as
> expected, for example, if they expect incomplete domain names in message
> headers to be qualified.  If this happens on 25 it's just plain wrong and
> it damages the mail transport infrastructure.  Mail should never be submitted
> on port 25 except in strictly controlled circumstances.  However until use of
> port 587 is more fully deployed we are stuck with a less than ideal situation.
>
> The decision to default to 587 and to eliminate the seperate port number
> field in Balsa's interface was not a frivolous one.  However the reasoning
> behind it requires a good understanding of the current mail RFCs and
> some idea of where libESMTP might go in the future.
>
> Brian Stafford
>
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