diff -r 3336e2f6fdef -r e155f2129514 artemis.py
--- a/artemis.py	Sun Jan 06 00:59:21 2008 -0500
+++ b/artemis.py	Sun Jan 06 01:06:52 2008 -0500
@@ -109,6 +109,7 @@
 	else:
 		msg.add_header('Message-Id', "<%s-%s-artemis@%s>" % (issue_id, _random_id(), socket.gethostname()))
 		msg.add_header('References', mbox[(comment < len(mbox) and comment) or 0]['Message-Id'])
+		msg.add_header('In-Reply-To', mbox[(comment < len(mbox) and comment) or 0]['Message-Id'])
 	mbox.add(msg)
 	mbox.close()
 
@@ -165,6 +166,7 @@
 		msg = mailbox.mboxMessage(properties_text)
 		msg.add_header('Message-Id', "<%s-%s-artemis@%s>" % (id, _random_id(), socket.gethostname()))
 		msg.add_header('References', mbox[0]['Message-Id'])
+		msg.add_header('In-Reply-To', mbox[0]['Message-Id'])
 		msg.set_from('artemis', True)
 		mbox.add(msg)
 	mbox.flush()
@@ -222,7 +224,7 @@
 	for i in xrange(len(mbox)):
 		m = mbox[i]
 		messages[m['Message-Id']] = (i,m)
-		children.setdefault(m['References'], []).append(m['Message-Id'])
+		children.setdefault(m['In-Reply-To'], []).append(m['Message-Id'])
 	children[None] = []				# Safeguard against infinte loop on empty Message-Id
 
 	# Iterate over children