Check out Send Mail in the File Menu. Look it up in FileMaker help to learn more. Check out the Email campaign management starter solution for more examples of how you might do emails from FileMaker.
Note if your are a Mac user and have the 11.03 version of FileMaker, you can send email via MS Outlook evne though it is not listed as a compatible email client program in the help file. Older versions--including 11.02 do not work with Outlook on a mac system.