Do not include conversation ID in references

Changelog.md

@@ -10,6 +10,7 @@ Changelog [format](http://keepachangelog.com/en/1.0.0/)
 ### Fixed
 * GODT-847 Waiting for unilateral update during deleting the message.
 * GODT-849 Show in error counts in the end also lost messages.
+* GODT-835 Do not include conversation ID in references to show properly conversation threads in clients.
 
 ## [IE 1.2.0] Elbe
 

pkg/message/header.go

@@ -84,10 +84,6 @@ func GetHeader(msg *pmapi.Message) textproto.MIMEHeader { //nolint[funlen]
 	}
 	if msg.ConversationID != "" {
 		h.Set("X-Pm-ConversationID-Id", msg.ConversationID)
-		if references := h.Get("References"); !strings.Contains(references, msg.ConversationID) {
-			references += " <" + msg.ConversationID + "@" + pmapi.ConversationIDDomain + ">"
-			h.Set("References", references)
-		}
 	}
 
 	return h