- Exit Outlook.
- Locate the Offline Address Books folder. In Windows 8 and Windows 7, the folder is located along the following path:
\Users\<UserName>\AppData\Local\Microsoft\Outlook\Offline Address Books
Note The folder may be hidden. To unhide it, click Start, type folder options in the search box, click Folder Options, click the View tab, click Show hidden files, folders, and drives, and then click OK.
- Delete the contents of the Offline Address Books folder. (The contents of the folder will be re-created when you restart Outlook).
- Start Outlook, and then test to see whether the issue is resolved by sending an email message as the distribution group.