Wikipedia:Emailing users

If you have set an e-mail address in your User preferences help, you can send e-mail to other users and receive mail from them through the Wikipedia user interface. In order to do that, visit the user's User page, and follow the "E-mail this user" link. The e-mail address you entered in your user preferences will appear as the "From" address of the mail, so the recipient will be able to reply.

Of course, if the user has openly published his email address, you can send him mail directly. Emailing users through Wikipedia is a privacy feature that protects your email address from spam.