Matching literal dot in To

I use the following to match a literal dot in the To field, the dot 
(period) has to occur prior to the @ character.  The recipe is:

"^To:.*\..*@.*"

For some reason, the recipe matches some (but not all, I have not found 
a pattern yet) addressees in the To field where there is no dot in the 
To address prior to the @ sign.  Logging shows the match occurring, but 
of course it does not give a reason why.

Any ideas on how to trouble shoot further?

Regards and thanks in advance for any help.

-- 
--Moby

They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety.  -- Benjamin Franklin