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
Sender / recipient validation
Charset / keyword filtering
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.