The example comment named check_sender_login() and strcasecmp; Postfix 3.7.11 compares the login in reject_auth_sender_login_mismatch() with strcasecmp_utf8 (src/smtpd/smtpd_check.c:3913, 3936). Found by the heuristics inventory - the rule's own example was written from memory. Says where the Debian sources are fetched from and kept. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>