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beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5

1 edit
reply to n0xlf

Re: Comcast blocked port 25 (SMTP)???

Ok for the above poster - having a SMTP server behind a router restricted to a lan is an open relay. There's no authentication other than not being accessible to the outside. Still open to your lan, so it's still technically an open relay.

No traffic is incoming on port 25 (unless you have a relay, which is still technically all sent messages), that would violate standards and the RFC's. So if you are processing 3000 messages a day, you are sending a boat load of email that should not be coming from a residential connection.
--
Tech at the Beach.
I speak for myself, not my employer.



n0xlf

join:2001-03-28
Castle Rock, CO
kudos:1

Having a public facing SMTP server is far different than one on a trusted network. Both are technically open relays, as you mention. (BTW, it wasn't behind a router - that's all part of sendmail config). Comcast used to allow (or maybe it was ATTBI) unauthenticated SMTP sessions that were simply allowed by IP, so at the time, having an open relay on a small trusted network was no biggie...

The second part of your message confuses me entirely. I do run my own relay, but the 3000 messages/day are incoming, which has nothing to do with "..technically all sent messages", RFCs, or "...sending a boat load of email". Incoming is incoming...It comes in on port 25, gets processed, and sits there. Beyond that, 3000 messages is nothing as far as BW is concerned.

In any case, the goal of my message was to point out a few other cases that may have not been considered for port 25 blocking. Comcast has traditionally been very tolerant of low bandwidth servers on residential connections, as evidenced by their lack of port blocking and scanning. The exception to this is port 25, which is an automated process for blocking. Obviously they still reserve the right to change their stance on enforcement at any time based on the AUP. They are far more concerned with bandwidth usage (server or not) on residential connections, as they should be...



beachintech
There's sand in my tool bag
Premium
join:2008-01-06
kudos:5

I believe port 25 blocking is more about curbing spam more than bandwidth. 3000 messages is thousands of times more than a normal residential user will send on average.
--
Tech at the Beach.
I speak for myself, not my employer.



n0xlf

join:2001-03-28
Castle Rock, CO
kudos:1

That's exactly what it's for...Again, the 3000 messages is received, not sent...



NormanS
I gave her time to steal my mind away
Premium,MVM
join:2001-02-14
San Jose, CA
kudos:11
Reviews:
·SONIC.NET
·Pacific Bell - SBC
reply to beachintech

Poster says he is RECEIVING 3,000 messages per day, not sending them. I was receiving close to that on one Yahoo! account, due to receiving "bounces" to spam sent as "from" that Yahoo! email address; even though I was not the sender (the email address was forged by the spammer).
--
Norman
~Oh Lord, why have you come
~To Konnyu, with the Lion and the Drum


supergeeky

join:2003-05-09
United State
kudos:3
reply to n0xlf

It seems very obvious to me that an APC SmartUPS which sends self-test emails once a week (1 that the test started, then shortly after 1 that the test completed ok or not) was "way too much" email, such that it triggers the SMTP block on Comcast connections.

...this has happened to me at about 20+ customers...

As such, I prefer to follow the rule of thumb that you shouldn't rely on port 25 on Comcast for any reason, because they can/will shut it off on a whim :-/

My solution in these cases is to setup a local SMTP server that uses gmail as the smarthost, therefor mail goes out over the more reliable port 587 or 465