How can I write a Gmail filter that matches on the number of email addresses in the “To” field?

Question

I'm trying to figure out how I can write a filter for Gmail that will match on the number of email addresses in the "To" field (plan to do the same for the "Cc" field as well, so if it counts both, that's a bonus.

What I want to do is match messages that have over say, 10 people in the To and/or CC fields, in order to catch mass forwards where the sender didn't bother to use Bcc. I can't seem to figure out a way to do this with the filtering options that are there. Am I overlooking something or is there really no way to do this?

Answer 1

According to GMail's advanced search help you cannot do that for now.

But maybe Priority Inbox is clever enough to categorize such emails as "not important". You can search for that with "-is:important" (the minus is for NOT).

An interesting option seems to be Syphir which connects to GMail and supports more complex rules like "How many recipients?" than GMail itself. Didn't try it myself though. Would be nice to hear back from you if you try that.