Currently, if a user does not have a correctly authenticated e-mail address set in their preferences, the "E-mail this user" link will not appear in the toolbox when visiting user or user talk pages. If they manually visit Special:Emailuser/Username, this message is shown:
No send address
You must be logged in and have a valid authenticated e-mail address in your preferences to send e-mail to other users.
Most users who have not set an e-mail in their preferences are new users. This is very difficult for new users to discover. Instead, I think the "E-mail this user" toolbox link should be shown regardless of whether they have a valid authenticated e-mail address, allowing them to reach the error page above, so that they know how to fix the problem.
Version: 1.19
Severity: enhancement