Unsubscribe from ALL Forum email?

Turn off all Forum notifications except for threads in which you've participated

Select an individual forum above (TV Forum, Internet, Phone, Apps).  

Then clickin the lower right of that forum's home page. 

(If you see, notifications for the selected forum were already off.  If you click it, notifications will be turned on for that forum).

Repeat for each forum you want notifications turned off.  It only has to be done once for each.

An alternative Settings method is described in Option 1 of this post.

Turn off all Forum notifications for threads in which you've participated

Select a thread in which you've participated and want notifications turned off. 

Then clickin the lower right of this page. 

(If you see , notifications for the selected thread were already off.  If you click it, notifications will be turned on for that thread).

Repeat for each thread you've participated in and want notifications turned off.  It only has to be done once for each. 

If you only want to stop receiving email notifications, see Option 2 in this post.

Note: Procedures listed are for Legacy Webmail, but the only procedure change appears to be step #3 is now "All settings ..." at the top, rather than "Settings" in a menu.