When troubleshooting AD related Exchange issues, a useful troubleshooting step is to work out which AD Site your Exchange server is in.
To do this, you should run the below command which will check which AD site your server is in for the litwareinc.com domain:
NLTEST /DSGETDC:litwareinc.com
If you find that your server is not reporting that it’s in the correct AD site, this can be the cause of your issues. You’ll need to check that your subnet to site assignment is correct using the Active Directory Sites and Services MMC snap-in.
Once done, you will need to check that your Exchange server IP is part of the correct subnet for the site it is meant to be in then restart Exchange to apply any changes.
More information on troubleshooting AD related Exchange issues can be found here.