The function findNewsletterID in check_bounce.php does a case sensitive match on Message-Id

The smtp server I use send me Message-id in the body, not Message-Id, so the line (427 in version 1.0)

$pattern = '/Message-Id\:[\s]\<([0-9]+)\..+\>[\s]/';

should be

$pattern = '/Message-Id\:[\s]\<([0-9]+)\..+\>[\s]/i';