We have some fairly advanced spam filtering at TMC but I am always cautious with spam, erring on the side of checking everything and not letting anything get deleted without checking it at least once. From time to time I miss an important message but I am getting a total of 1,000 messages a day when you sum it all up so checking this mess is time consuming. We have the option to delete items marked as spam and I don’t do this unless the sender is on a blacklist. Blacklists are centrally maintained and this system is pretty accurate. Every now and then a real message gets flagged as spam.
Anyway, I wanted to share a tip. One of our spam filters — yes we have a few on the server and locally, on each machine — changes the subject line to tell you why the message is marked as spam. I have been noticing more and more Cyrillic spam and the subject of all these messages now have the word Cyrillic in them. I just made a rule that takes these messages and deletes them. Spam has been reduced a great deal.
I still check the deleted folder (I have to permanently delete something for it to go away) from time to time but out of a few thousand Cyrillic messages, not one of them has been legitimate so far. The same can be done will characters in other languages. Good luck and happy spam hunting.