What characters can be in an email address?

Not sure if there's an RFC on this (Era will know I'm sure ;-) but I was  
wondering what non a-z 0-9 characters are considered "legal" as part of an  
email address.... or maybe what aren't?

I know/guess that

        @ ! , " ' < > ( ) %  are not allowed

        + _ . *
        
What about others such as ? / [ ] ~ ` & = # ^ : ;


Just curious....

Thanks!

TjL