If your reciving errors downloading Offline Address Book either from internal or external environment you may receive this error below or something similar.
1. Open your Outlook 2010
2. Once open, while pressing CTRL button, click on the Outlook icon on the bottom right hand corner
3. You will see a menu, Click on Test Email AutoConfiguration
4. You will see image below, fill in the problematic email and password. Make sure to uncheck USE GUESSMART and SECURE GUESSMART AUTHENTICATION.
5. Once you receive results, analyze and confirm OAB URL is pointing to HTTPS://mail.domain.com/OAB/xxxxxxxxxxxxx where xxxx represents several random letters and numbers
6. Next, Log in to Exchange Server, if roles are split, make sure your you log in to the Mailbox Server, open Exchange Management Console
7. Click on Mailbox under Organization Configuration
8. Click on Offline Address Book tab
9. Right click Default Offline Address Book, click Update
10. Now you will navigate to Offline Address Book files folder, click on Start, Computer, C Drive, Program files, Microsoft, v14, ExchangeOAB
11. If ExchangeOAB folder is missing, you may need to create manually. Now check the timestamp on the files, make sure it is being updated. Now click on the back button until you get v14 folder. Double click on ClientAccess folder and look for the latest one to check timestamp on files.