What do you mean by "sending out"? Do you want the visitor to be able to configure the recipient or do you want to use a fixed one?
If you _need_ it "open", I'd require at least registration, and use a strict check of the mailaddress that it must match against, not just a search for malicious contents.
Maybe you could get a bit more clear on what you're on to? :)
Ordinary morality is for ordinary people. -- Aleister Crowley