Just a quick suggestion.. I have others, but this should be quick to implement-
Could there be an option to Send Queued Mail on Exit? All emails that have been generated during a session could be sent when the program is closed.
I use a Mail Notification software in my system tray, so I never check for mail unless I know I have some waiting (there are others who do this as well). Often I have forgot to explicitly send email, and wonder why I haven't received a response.