message-is-yours-p
message-is-yours-p is a compiled Lisp function in `message.el
'.
(message-is-yours-p)
Non-nil means current article is yours.
If you have added 'cancel-messages to `message-shoot-gnksa-feet', all articles
are yours except those that have Cancel-Lock header not belonging to you.
Instead of shooting GNKSA feet, you should modify `message-alternative-emails'
regexp to match all of yours addresses.