One of my users was having trouble with Synchronizing email on their PDA over ActiveSync with Exchange Server 2007. Looking into the entry it looks as if the domain is set incorrectly however the username and domain fields are greyed/grayed out and won’t allow change. The only way I could find around this was to go into the Start, Programs, ActiveSync menu then select Menu then Options. This brings up a summary of the connections and folders; click on Exchange Server then click Delete. Back on the ActiveSync menu it is then possible to add a new mail source.

IMPORTANT! Use this tip with care as it will remove all the relevant mail settings on the PDA.