By default, Microsoft Windows HTTP Services (WinHTTP) will try six IP addresses (one initial attempt and five retires) to establish a connection to a host. However, if Microsoft Outlook 2013 and Outlook 2016 try more than six IP addresses, the connection will fail. This is particularly true on networks that have intermittent IPv6 connectivity problems. The increase of the number of retries makes sure the success of the connection by using IPv4 addresses. To enable this feature, install the following updates and then follow the steps.
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 10, go to Start, enter regedit in the Search box, and then select regedit.exe in the search results.
- In Windows 8 or Windows 8.1, move your mouse to the upper-right corner, select Search, enter regedit in the search text box, and then select regedit.exe in the search results.
- In Windows 7, select Start, enter regedit in the Start Search box, and then select regedit.exe in the search results.
- Locate and then select the following registry subkey:
- On the Edit menu, point to New, and then select DWORD Value.
- Enter MaximumConnectRetries, and then press Enter.
- In the Details pane, press and hold (or right-click) MaximumConnectRetries, and then select Modify.
- In the Value data box, enter 1, and then select OK.
Note Outlook 2013 and Outlook 2016 use this value to set the number of WINHTTP_OPTION_CONNECT_RETRIES for requests when MAPI/HTTP connections are used.
- Exit Registry Editor.