Command - /NickServ SET SHOWEMAIL
Usage   - /NickServ SET SHOWEMAIL [ON/OFF]
When enabled, your e-mail address will be shown to people using the NickServ INFO command.
Note: You must be identified to NickServ in order to use this command.
Example(s):
/NickServ SET SHOWEMAIL ON
/NickServ SET SHOWEMAIL OFF