North American Network Operators Group

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RE: Misguided SPAM Filtering techniques

  • From: David Schwartz
  • Date: Tue Oct 23 21:33:37 2007

Dave Pooser wrote:

> We had a client whose RFP vanished into thin air because of that-- he sent
> it from a hotel that practiced port 25 hijacking and had had their IP
> blacklisted for spewing much spam and viruses. So our server rejected the
> message, and when it tried to send the NDN to him *his* server
> rejected the
> NDN for the same reason. Fortunately he called the next day with some
> details he'd omitted....
> I recommended he go back with an army of Huns and raze the hotel, but he
> settled for a nasty letter and using 587/TLS in future.

You should have used the oppurtunity to educate your customer. Email is a
best-effort, no receipt service. It is simply not appropriate to use for
business-critical communication without some kind of confirmation of

The hotel didn't really do the wrong thing. It took the email and made a
best effort to deliver it. When it failed, it made a best effort to alert
the sender. That is what email is supposed to be like.

Obviously, they've had a spam problem. So just passing port 25 unmolested
would not be right. Blocking it is not a very good solution either because
people who are not sophisticated will just be unable to send mail. People
who are sophisticated won't be using port 25 outbound from odd net locations

You should blame whoever decided not to accept *any* email from the hotel
just because *some* of the email was spam. That person knew or should have
know that some of that email might be business critical. Hmm, that was

Perhaps you are using a misguided spam filtering technique? How many RFPs
are you willing to lose to reduce spam?