Is there a token for the email used in a CiviMail mailing?
This token doesn't exist as a CiviCRM token.  However, if you're using Smarty rendering for CiviMail then you can use the Smarty tokens,which wil include the email address.

While Smarty rendering will add overhead to CiviMail, so does rendering non-contact tokens.  I'm not sure which way will be faster - or if that matters to you.