At 6:20 AM -0400 4/12/05, Larry Seltzer wrote:
I had a thought yesterday that I wish I had before I hit the publish button
on the article: Perhaps the answer for people who need an exception case for
port 25 blocking is port 587
Yes, in most cases. Port 587 is the standard port for initial mail
submission, a protocol so closely related to SMTP that most MUA's
don't even have to know that they are speaking it instead of SMTP.
People who are not doing initial mail submission and want port 25 for
things they should not try to do on port 587 instead probably should
not be doing that from a dynamically assigned address anyway, unless
they have deep support from their ISP for that sort of use, including
dynamically assigned reverse DNS records and other such oddities only
witnessed in corporate networks and dreams born of jalapeno and
anchovy pizza...
or even some non-standard port.
No. Please no. I beg you: do not suggest the use of 'some
non-standard port' for anything in a published article.
I checked and
my own mail server supports both.
Any modern MTA worth using will support port 587 use, and most will
allow you you put the listener on any arbitrary port. The latter
should be reserved for carefully considered and highly unusual
circumstances.
Put SMTP on port 1125 or something like
that for your external users,
Please, no. There are standards for using non-standard ports. Using
otherwise assigned ports is a generally bad idea.
or use 587 and require authentication. Is
there a reason this wouldn't work?
Sturgeon's Law always applies, but there is no other reason I've seen.
Yes, people use garbage MTA's and/or firewalls and/or configure one
or both poorly. At least one ISP briefly has blocked port 587 out of
what can most charitably described as overzealousness.
I'm also going to contact SBC and ask them how their opt-out system is
working so far.
Based on the traffic in the private sbcglobal.help.* newsgroups, it
seems to be working well, but of course the population of people who
would manage to share experiences there is likely not a random
representative sample. A somewhat differently skewed sample of 19
people working in an IT firm with SBC DSL accounts found 2 with
static accounts (no block) 1 who used the preemptive opt-out
successfully, and 3 who think their machines got faster since the
first of the year.
On the negative side, those same SBC (user to user) help newsgroups
have shown some reports of what looks like SBC cutting off users from
the smtp.$SBCUNIT.yahoo.com mail servers that are part of the
SBC-Yahoo unnatural act.
--
Bill Cole
bill(_at_)scconsult(_dot_)com
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