On Mon, Feb 13, 2017 at 08:41:51PM -0800, Junio C Hamano wrote: > Arif Khokar <arif.i.khokar@xxxxxxxxx> writes: > > > One concern I have regarding this idea is whether or not SMTP servers > > typically replace a Message-Id header set by the client. > > The clients are supposed to give Message-IDs, but because some > clients fail to do so, SMTP server implementations are allowed to > add an ID to avoid leaving a message nameless (IIRC, 6.3 in > RFC2821). So "replace" would be in violation. > > But some parts of the world ignore RFCs, so... I know there are some terrible servers out there, but I think we can discount any such server as horribly broken. Rewriting message-ids would cause threading problems any time the sender referred to their own messages. So "format-patch --thread" would fail to work, and even replying to your own message from your "sent" folder would fail. -Peff