Try all of the tools I specified. I had success with all of them.

Nessus would be the best one of all but I have no idea where your scanner is, what version you have, what plugins you're using, etc., etc.

Your other option is to give someone permission to hit your server from the outside and hand you the results. Many folks here have the ability to do this for you. All you have to do is ask in writing and assume all responsibility of failures of any kind.

--Th13