March 13, 2008
We have recently added the Sorbs blocklist to our antispam measures. Prior to this we have been using a combination of the Spamhaus sbl and xbl lists, with a mimedefang setup. This initially proved very successful, however, this year and in particular over the last month, we have noticed yet another sharp upturn in the amount of spam hitting our servers. Currently at least 97% of all email hitting our servers is spam. That is, we are currently blocking around 97% of all emails trying to be delivered to our servers. The 3% that gets thru still contains some spam, so the figure is actually higher than 97%, but not so easily quantifiable.
As a result, we have had to have another look. Among the first things we tried was the addition of the Sorbs blocklist and were surprised at how big a difference this has made. No doubt though it will only be a matter of time before the spammers come up with a way round this too, or simply increase their volumes to compensate for the lessened success. So we are currently evaluating the open-source ASSP system, which appears to be exceptionally highly valued by current users.
Here is what the Sorbs list considers to be spam:
SORBS' definition of spam
SORBS considers Unsolicited Commercial Email (UCE) to be spam.
SORBS considers Unsolicited Bulk Email (UBE) to be spam.
SORBS does not consider any solicited email to be spam.
SORBS does not consider Unsolicited Email that is not Commercial or Bulk to be spam.
This means that advertising messages as part of a so-called "opt-in mailing" list will be classified as spam if they are received before a non-repudiatable confirmation of that opt-in, sent by the true owner of that address, has been received by the management of that mailing list. Further, if the opt-in confirmation request appears to be an advertisement for products and services other than the mailing list itself, it will also be considered spam.
As for ASSP, we are currently training it on a development server, and will evaluate it fully in a matter of days. If we are as happy with it as many of its current users appear to be, we will implement it progressively on our servers over the month of April.
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