This might be usefull if you would like to force people coming back to the forums to read their subscriped threads instead of having all the information already send by email.

AdminCP -> Languages & Phrases -> Search in Phrases

Search for notify in Phrase Variable Name Only.

Click Edit for the phrase Email Body Text Phrases Containing 'notify'

Copy the entire phrase but remove

Code:
Here is the message that has just been posted: *************** $pagetext ***************
and paste it into English (US) Translation (Optional) and save it.

People are now forced to return to your forum to check the threads they have subscriped.