Interesting scenario this week. A message sent within my Exchange Organisation on 26/10 only arrived at the recipients mailbox today (07/11). The message was sent from a mailbox on a server inour French office within the Exchange Organisation. Interestingly, on my mailbox store here I archive all messages sent or received by mailboxes and this showed the message being received at the time it was sent, meaning it must have reached my Exchange Server suggesting to me that it is an issue on our Exchange Server. Why then would it only be delivered after all this time to the actual mailbox!?
Unfortunately Message tracking was not turned on on either of the Exchange Servers. If a message is sent now it is delivered straightaway to the mailbox.