Remove contacts from synced Exchange account, without removing them from the server
There's 2 slightly different solutions. 


Log onto your corporate mail account using Outlook Web Access. Go to the account settings, i.e. the options link. Under that, select Phone, and delete your phone profile from there. 
Now delete &amp; recreate the Exchange account on your phone, and this time don't choose to sync contacts. 
Exchange has a corporate addressbook or directory, and a local addressbook for your own personal contacts. Get rid of the locally saved contacts in your Exchange addressbook, so that on the next sync they'll similarly be culled from the phone. You can always look them up in the corporate directory, and Android can also perform a lookup against the directory for contacts that aren't stored locally. This of course assumes that you don't actually need so many contacts on hand in your local addressbook, or that these are all company contacts and not external business contacts.