> On Sep 25, 2023, at 06:52, Teemu Likonen wrote: > >> Some person on debian-user mailing list seems to be sending messages >> with fixed Message-ID field: the same ID in different messages. In >> Notmuch it is creating trouble because it connects unrelated threads to >> one. The person has different messages in different threads but Notmuch >> thinks they are the same message because the Message-ID is the same. >> >> This is potentially a "denial of service" for Notmuch. Well, not quite, >> but is harmful nonetheless. How would a Notmuch user fix the mess or >> protect himself against it? > > I am no longer sure if this issue is caused by fixed "Message-ID" or > wrong "References" or "In-Reply-To" values. Anyway, someone has created > real mess anyway because Notmuch combines originally separate threads > now and forever. Silly question, I know, but have you actually tried reaching out to the user? No MUA that I’m aware of acts like this and it’s pretty clear from documentation and standards tracks that Message-ID is meant to be globally unique per message. If the user is knowledgeable enough to have a boutique mail reader, they’re probably also knowledgeable enough to correct the defect too.