Comment 2 for bug 266323

You can suppress sending confirmation by putting the
victim's email address in ban_list from the admin page
(privacy section), if she/he is not willing to be added in
your list. This may not work if the malicious user forges
the 'From:' header. In this case, the victim may well
introduce some mail filter to get junk mails discarded
before they reach her/his eyes.