Enable feature "Subscribe to this forum"

Hi,

I read in the manual there is a possibilities for my members to subscribe,
But which command in which file do I have to turn on?

Dominick

Members could subscribe only to the certain topic, not the forum in whole. Take a look at the $emailusers option, it should have either 1 or 2 as its value.

Here is the similar thread/question:

How to get the choice "Check to watch this topic and get updates by email" ?