Lua primitives: on_message_aborted()
If you define the function on_message_aborted it will be called when a message isn't sent.
Send mail? y/n/a>
Valid options are:
Send the mail.
Abort the sending.
Add an attachment.
The second option, "n", will cause this hook to be invoked, if it is defined.
This function has been available since version 0.16.