Dear,
I was requested to develop a notes client plugin to do some checking (like the spell checking) before the email sending. My basic understanding is to trap the click event of ‘send’ button/menu, but can not find how to do it…
or any other approaches? thanks a lot! 
Subject: comment
trapping the button is not enough (although you can do it - look at the “Save and Send” action in the Appointment form), because the user can also send by hitting Escape, and then saying “yes” to the prompt.
Otherwise, you need to write your own version of SendPrimaryRequest to run before the standard one in CSEventNotes library.