Running support: tickets, threading & replies — How a reply finds its way home

Every message RowFold sends sets its reply address to t-{mailboxToken}+{recordId}@… — the table's own inbound address with the ticket's id sub-addressed onto it. That is the primary mechanism because it survives mail clients that strip threading headers, and plenty of them do. When it is missing, RowFold falls back to the headers: In-Reply-To first, then the References chain read from the nearest ancestor outwards, matched against messages it has actually seen. Matching on the subject line is deliberately not implemented. Re: Invoice from two different customers is the classic way support systems cross-contaminate threads, and a wrongly merged ticket shows one customer another's conversation. The address is the primary mechanism rather than the threading headers, because plenty of mail clients strip those.