Is SharePoint prompting your users to login when they are in the office or opening documents from SharePoint? There are a couple of things you can try:
1- Added SharePoint site to Intranet Zone
On the Users Internet explorer go to:
- Tools > Internet Options
- Select the Security Tab
- Select the Local Intranet zone then click Sites
- Click Advanced
- Add the SharePoint URL then click OK
- Click on Custom Level then scroll to the user authentication section at the bottom
- Set it to Automatic logon with current user name and password
2- Registry
Adding this entry allows the users login to be forwarded to the server you specify.
- Open Regedit
- Navigate to: HKLM\System\ControlSet001\services\WebClient\Parameters
- Add a new Multi-String Value: AuthForwardServerList
- Data: http://sharepoint.domain.local
- Reboot