Ismail

Does the same functionality as BuddyPress, emailing users who get mentioned in a bbPress topic or reply. The aim of this plugin is when to enable that feature when no BuddyPress is there. 
To do: – warn user about bbPress/BuddyPress presence

bbPress Mentions Email Notifications

Adds the @mentions to bbpress - really useful

Great plugin

Email bbPress topic/reply mentioned users, set custom email and some basic settings

cubecolour

WordPress 4.5 added the ability to login using the registered user’s email address in place of the username. When this plugin is active, the ability to login using the email address in place of the username is removed, and the label of the input field is changed to reflect this.

No Login by Email Address

Removes the ability to login using the email address instead of the username.

bbPress Mentions Email Notifications vs No Login by Email Address