Follow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.
- Exit all Microsoft Office applications.
- Start Registry Editor:
- In Windows 7, click Start, type regedit in the Search programs and files text box, and then click regedit.exe in the search results.
- In Windows 8, move your mouse to the upper-right corner, click Search, type regedit in the search text box, and then click regedit.exe in the search results.
- Locate and then select the following registry subkey:HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook
- On the Edit menu, point to New, and then click DWORD Value.
- Type AllowUnknownExAttendeesOutOfDate, and then press the Enter key.
- In the Details pane, right-click AllowUnknownExAttendeesOutOfDate, and then click Modify.
- In the Value data box, type 1, and then click OK.
- Exit Registry Editor.
Article ID: 3054850 - Last Review: 12 May 2015 - Revision: 1