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SpamSentinel Now Blocks Spam at the SMTP Level

So, in reply to some of my postings,
many people replied that they want to stop the spam at the SMTP connection
layer, a feature RBLs provide. You want to cut down traffic and work on
the Lotus Domino email server.

We hear you loud and clear.

In a frantic week of development and
testing, we have enhanced SpamSentinel to reject spam during the SMTP connection.

And the results are truly fantastic!

On our inbound SMTP gateways, SpamSentinel
v 7.5 stops over 90% of email received during the SMTP connection but before
the mail is accepted. This is a full 10%, better than any RBL (I tested
with Spamhaus and Spamcop, which together averaged 78%). The remaining
12% is picked up and caught as spam at the Domino server or as a virus
using our Norman anti-virus checking.

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There are two ways to stop mail at the
SMTP gateway: Silent Delete and Reject. The silent delete does not give
any information to the spammers. We let them connect, and 88% of the time,
we terminate the SMTP connection without saving the message. The other
method is a PERMFAIL (we use the generic 554 PERMFAIL option), which rejects
the SMTP connection. Given that most spammers do not really exist, and
that our SMTP servers are talking many times to a BOT, I prefer the silent

In our tests, this is blazingly fast,
and reduces bandwidth and server activity significantly.

No False Positives in Rejected Mail

v 7.5 also has no false positives in
what it rejects. This is based on actual experience for Spam-D classification
which is in use across thousands of servers and based on hundreds of millions
of messages processed. If SpamSentinel does make a mistake, it would show
up in the Quarantine as Spam-B or Spam-C. Because this is a Lotus Notes
database, users can retrieve these blocked messages.

Anyone who wants this version right
away, email me
and I will get you the

Daily Spam Statistics

Here is a snapshot of the daily statistics
for one of our actual SMTP inbound servers. The results on this server
are better than 88%, as it is the second SMTP server, which gets mostly
spam, so 92.5% of messages were silently deleted. Most people should expect
88-90%. The 4,764 messages that our Domino server has to process brings
us back to the levels of spam received in early 2005!

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Frank Paolino's picture

Frank Paolino is the Founder and President of Maysoft, Inc. He likes to blog about Email security, email viruses and general email management.