Notification mail for issue and MR threads carries Reply-To: reply+<token>@<domain> when the instance has [mail.inbound] configured and the recipient turned notifications settings reply on. gitbayd polls the mailbox over IMAP with TLS (no open port; password from a file). A reply posts through the comment command as that user when the HMAC token (bound to user, repository, thread, expiry, and refused for ids reused since it was minted) checks out, the From address is one of their verified addresses, and, with trusted_authserv_id set, the host's Authentication-Results show aligned DMARC or DKIM (RFC 8601 parsing, public-suffix alignment). Quoted text and signatures are stripped. Refusals send nothing back and are audited without content. The IMAP client bounds what a server can make it hold. Off by default. Migration. Admin/Users/Threat-Model/Parity/CHANGELOG; fuzz targets in audit.sh.
Closes #295