Message time is days before message tracking logs show it was received.

Environment: Exchange 2013 CU7

I have a user who is reporting that she sent a message on 1/6/2015 to an internal Exchange recipient from her Outlook client.  I have seen the message from the mailboxes and it shows the correct date.  However, they said the message didn't arrive in the recipient mailbox until 1/9/2015.  I ran a get-message tracking log and it shows the server received it and delivered to mailbox on 1/9/2015.

Does anyone have any ideas on why the message would show 1/6 but the server didn't get it until 1/9?  

Thanks,

Jeff