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I'm having a bit of an issue with a recent spam wave on my network. We're using a variety of e-mail checks that have been quite successful thus far, but these e-mails are presenting a problem.

They come with no subject line and read a something like this

I just scored $128 in a day doing simple tasks! I went to - Business Week Journal Dont forget to thank me! right arm and leg and the whole side of his face are paralysed. and their swords, can boast a record that mushroom growths like the no means satisfied with the relation I gave him of the manner I he may have used my knowledge for his ends.

My staff are great at spotting spam (and quite frankly this isn't too hard to pick out as being illegitimate e-mail) but they're quite annoying and have a link to (what I presume to be ) a malicious / phishing site.

Information about the e-mails

  • They are all coming from free e-mail providers like hotmail, yahoo or gmail. As such, they pass many tests that our anti-spam uses.

  • The e-mail addresses never "re-offend" in that one e-mail address will never e-mail the message again. Blacklisting e-mail addresses is a waste of time.

  • The subject line is always blank, so we can't use keyword blocking like we've done with other spammers (use your imagination as to what our keyword list looks like...)

  • The e-mails are sent in a western charset so charset blocking is not possible.

Tests we currently use are

  • RDNS

  • DNS Blacklists

  • SPF Test

  • Sender / recipient validation

  • Honeypot

  • Charset / keyword filtering

  • HELO blacklist

  • IP / e-mail blacklisting

If you guys could offer some advice I would really appreciate it. Please note that we're a small company and don't have the money to invest in large enterprise solutions.

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Possibly a silly suggestion- but how many legitimate emails do you get with no subject line? Could you just block all emails with no subject line?

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Not a silly question at all but unfortunately my CEO sends quite a few e-mails with blank subject lines. That idea had already crossed my head :) – DKNUCKLES Dec 13 '10 at 16:30
What your CEO sends shouldn't matter as long as you are only utilizing that rule to block mail coming into the network from external email providers. In other words, if you set this rule up in a spam filter then users internally wouldn't ever hit the rule unless they were mailing something from a personal account which isn't something you really want anyway. Of course this will block some legitimate mail with someone's spouse sending him an email or something or other so it isn't ideal - but it shouldn't affect your CEO. – Charles Dec 13 '10 at 17:00

This is a pretty good free product for blocking SPAM It also comes with Web filtering and Anti-virus

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