The following hooks are currently available: 

These hooks are always executed as soon as a reminder mail is sent.
The hook files can be found in the module directory at the subdirectory "hooks".

After Send Mail

You can execute custom code after a mail has been sent.

Before Send Mail

With "logActivity (json_encode($MailVars))" you can get an overview of all mail variables. 

Setting "$abortMail" to "abort" does abort sending the current mail.