Now that we have internal_date on all messages, we should be using it

for sorting. This will prevent spam with ...less true dates from pushing
messages to the top of your list. Additionally, when downloading
messages from the server, they'll actually appear in the order they were
received - the existing behaviour really screwed up users who were
trying to triage mail as it came in.

src/com/fsck/k9/activity/MessageList.java

@@ -2445,7 +2445,7 @@ public class MessageList
             {
                 LocalMessage message = (LocalMessage) m;
                 Date date = message.getSentDate();
-                this.compareDate = date;
+                this.compareDate = message.getInternalDate();
                 this.folder = folder;
 
                 if (Utility.isDateToday(date))