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ISPs blocking port 25 on their networks


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IMO it's good news, as long as those who have a

legitimate use of the port are still alowed to use it.

Comcast takes hard line against spam

By Jim Hu

CNET News.com

June 10, 2004, 12:56 PM PT

URL: http://zdnet.com.com/2100-1104-5230615.html

Comcast, the nation's largest broadband Internet service, this week began selectively

blocking a network loophole commonly exploited by spammers.

The cable giant, whose broadband Internet service has more than 5.7 million

subscribers, said it will block what's known as "port 25" for accounts suspected of

sending mass amounts of unsolicited e-mail. The company will implement blocks based

on subscriber accounts with the most outbound activity.


my questions to you all are "is it a good step?", and "have you noticed a difference?"

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It should not reduce functionality because most of their AUP's specifically state no servers are to be run on the connection, which would include mail servers.

It is simply enforcing the rules already in place.

As far as helping, I have not noticed many comcast reports lately and they have moved down to #4 on the Hall of Shame after being either #1 or #2 solidly for a while. Also, at this moment, only 6 reports to them in the last 17 minutes.

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We use the corporate mail server for all outgoing mail, especially employee to employee. Its set up to use SSL on both ends of the connection, so man-in-the-middle attacks will have to break the SSL as well, not just listen to conversations.

The other reason is so that our sales staff does not have to mess with settings while on the road. They always go through our server. This gives us better security over what would be otherwise be wide-open communication.

Losing port 25 is no big deal for us, but it could be a PITA for others. If so, just open the submission port on your mail server and let them use that in place of 25.


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The number of reports I'm submitting to Comcast has dropped significantly in recent days so it seems to me either that Comcast's action is being effective or the spammers have gone elsewhere 

Just looked at my logs and Comcast has been fairly stable over the last couple of months, and we've been SCBL'ing 150-200 every day (another 50 or so with other BL's). If they have made a difference, its not showing up in my numbers at all, at least nothing significant. Would be nice to see a drop.


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