In Site manager -> Development -> E-mail templates, you can find the following e-mail templates:

 

Friend approval - template for e-mail or message confirming that a user approved your friendship request

Friend rejection - template for e-mail or message confirming that a user rejected your friendship request

Friend request - template for e-mail or message notifying you about the fact that some user requested your friendship

 

If you choose to Edit () some of the templates, you will see two large text fields:

 

Text - text of the template used for e-mails

Plain text - text of the template used for messaging module messages

 

Page url: http://devnet.kentico.com/docs/devguide/index.html?friends_available_e_mail_templates.htm