Email filtering

I have quite a few filters set up on my email address to help address things like spam, but I also have some set up for specific tasks, in one case, filtering Microsoft Office files.

Basically the filter is Message body contains 'attachment' AND either '.doc' or '.docx'. Then it will redirect the message to another mailbox for me to peruse at my convenience, and will send a failure to the sender.

If the message body contains testfile.doc, it works. But if the message body contains "testfile.doc" (with quotation marks), it doesn't work.

Any idea why the quotation marks seem to have an effect? As I selected 'contains' in the filer, I would have thought that both testfile.doc and "testfile.doc" would work, as they both contain .doc.

I've attached a screenshot of the filter.

Attachment 1036

- - - Updated - - -

OK, someone on IRC just told me to do the .doc and .docx as two separate filters rather than one filter with the OR, and for some reason that seems to work.

Any idea why one way works but not the other?