I am on a number of mailing lists - they work like this
If john posts to the mailing list
mlist@test.com the mail arrives into the inbox as being from John but sent on behalf of
mlist@test.com- in thunderbird
mlist@test.com is the sender.
I want to be able to do a search for mails of this type something like sender:mlist@test.com so I can easily archive them.