Messages stil showing unread on iPhone

Hi All,

One of my email accounts is exchange server - and even when i read all messages on my computer - my iphone and ipad still show messages as unread.

How do I resovle this?

Alternatively is there a setting that I can select the whole inbox and say show as read (ike in outlook) on my iphone? Or do I have to go one by one to read all the messages? there are over 100 messages going back a month.

Regards

Manoj