DALnet Services Help — NickServ → SET SHOWEMAIL.
Nickserv
DALnet's nick registration service allows users to register a nickname by providing a password, preventing other users from using it. NickServ registration is required for such things as registering channels and sending/receiving memos.
This option allows the user to choose whether or not regular IRC users gets to see their email address set during registration or via /nickserv set email
Command: /nickserv set SHOWEMAIL (on/off)
Example: /nickserv set showemail off