North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: ingress SMTP

  • From: Justin Scott
  • Date: Wed Sep 03 11:57:02 2008

What is preventing this from being an operational no-brainer,
including making a few exceptions for customers that prove they know
how to lock down their own mail infrastructure?

As a small player who operates a mail server used by many local businesses, this becomes a support issue for admins in our position. We operate an SMTP server of our own that the employees of these various companies use from work and at home. Everything works great until an ISP decides to block 25 outbound. Now our customer cannot reach our server, so they call us to complain that they can receive but not send e-mail. We, being somewhat intelligent, have a support process in place to walk the customer through the SMTP port change from 25 to one of our two alternate ports.

The problem, however, is that the customer simply cannot understand why their e-mail worked one day and doesn't the next. In their eyes the system used to work, and now it doesn't, so that must mean that we broke it and that we don't know what we're doing.

Your comment about "exceptions for customers that prove they know how to lock down" is not based in reality, frankly. Have you ever tried to have Joe Sixpack call BigISP support to ask for an exception to a port block on his consumer-class connection with a dynamic IP? That's a wall that I would not be willing to ask my customers to climb over.

Now, having said all that, I do agree that big ISPs should do more to prevent spam from originating at their networks. A basic block of 25 isn't the solution, in my opinion. Unfortunately I don't know what is. Perhaps monitoring the number of outgoing connections on 25 and temporarily cutting off access if a threshold is reached? Set it high enough and the legitimate users won't notice, but low enough that it disrupts the spammers. Perhaps I'm talking out of my ass and don't have a clue.

In any case, I don't believe a blanket block of 25 is the answer.

-Justin Scott, GravityFree

Attachment: smime.p7s
Description: S/MIME Cryptographic Signature