Client Outlook not updating email from Exchange

There are basically two workstation that are connected to a exchange server. Now the problem lies in both the client system. It is not able to collect email updates from MS Exchange Server. Others are working fine. But only this 2 systems fails to update. The problem started after a power failure at my office. The last email that are visible on the system is date before power failure. I had tried to re-add the exchange server account but still the problem lies the same. I am not able to work on the same. Other workstation looks to be working but only two failed to work.

Does new installation is working or not. I think you must do that. But before that just backup your mailboxes. Export them and keep it safe somewhere. Later on you can try to re-install SBS server back from scratch and see whether it is working fine or not. With new installation you can simply reconfigure the installation and check the mail box are working fine or not.