Slow and delayed emails coming in............

I use outlook 2007 and for the past 2 days my email have been coming in delayed. Some come over on time and then say around 6pm I will have emails in my inbox that just came over but have a time stamp of 9am. For instance my mail just updated at 10pm and in my box was an email timestamped for 9:23am and it just showed up in there. I've rebooted, ran virus scan, everything is fine and still doing it.