Random emails not in Outlook but in OWA Outlook 2010 Exchange 2010

view story

http://serverfault.com – I have a single Exchange Server 2010 SP2 RU6 with about 50 mailboxes that is running in single site/domain without any major concerns. Nearly all clients are Windows 7 running Outlook 2010 Professional (x86) (some SP1, some not). I have only one client that is experiencing issues with Outlook. It seems that they are randomly not getting emails until days later. The delayed emails can be group/individual, internal/external, it doesn't matter. It seems to be about 1-3 emails per day that don't arrive on time. I've been having the user login to OWA every morning to check their inbox v. Outloo (HowTos)