Hi, I'm looking into taking the References header into account for thread ordering. So far only In-Reply-To is used. My C/C++ is rusty at best, so I'd need some help to get this done. Carl gave a try on irc already to clear things up for me, reading into it, I have more questions: lib/thread.cc/_resolve_thread_relationships adds messages as replies to a parent. Currently, we seem to treat In-Reply-To as empty or single msgid. If I understand rfc822 it can be a list of msgids and/or phrases. Do/shall we support that? References is a list of msgids, with the last one being the direct parent. I don't know how multiple direct parents are handled here. DJB recommends "... readers look for identifiers in In-Reply-To and append them to References if they are not already included in References." [1] In that case if there are two msgids in In-Reply-To and there are appended to the References list, than only the last one will be a parent and the one that used to be the last is not a parent anymore. And Carl recommends to treat references and in-reply-to as two separated sources of information, first using in-reply-to and then references in order "to attach to the deepest referenced parent". I fail to understand that. Am I complicating things? How do we want to treat the combination of References/In-Reply-To? Do we have code that returns the last msgid listed in references? database.cc/parse_references seems not to care about order, just existence - or is GHashTable ordered. [1] http://cr.yp.to/immhf/thread.html florian -- Florian Friesdorf GPG FPR: 7A13 5EEE 1421 9FC2 108D BAAF 38F8 99A3 0C45 F083 Jabber/XMPP: flo@chaoflow.net IRC: chaoflow on freenode,ircnet,blafasel,OFTC