Mail for Exchange stops working when there are too many emails in the inbox

Today my Mail for Exchange 2.7 (symbian) just stopped working. When I started the synchronization, it just showed error. I noticed that my inbox contained around 420 emails. I then went to the web interface of my Exchange provider and moved all the emails in my inbox into my archived folder and then everything just works! This maybe a limitation of Mail for Exchange 2.7!