We use ACT to send "mail merged" emails, among other things.
When I train new users how to do mail merges, I always pause when we reach the last step of the mail merge wizard - step 5 of 5, entitled "Completing the ACT! Mail Merge Wizard."
And I say, with as much drama as I can muster:
"This is the #1 stupid thing in ACT!. This window does not make it obvious that when you click Finish, you actually send the emails out. So do NOT click Finish if you are not SURE that everything is good and ready to go. WHEN YOU CLICK FINISH YOU ACTUALLY SEND THE EMAILS."
And I repeat that twice.
I do that because we had several (!) folks send out mail merges to LOTS of people unintentionally.
Please make it more obvious that clicking Finish actually sends the message!