Outlook on the web shows the mobile devices that you use to connect to your mailbox. If you're no longer using a device or a device isn't syncing properly, you can delete it from this list. Doing so removes the partnership between the mobile device and your mailbox, but doesn't delete the email account from your phone. Removing this partnership following the steps below often fixes sync issues.
If you're using Outlook on the web and your device still won't sync or you're having connection problems, see Using the Microsoft Support and Recovery Assistant for Office 365.
Sign in to Outlook.
Tip: For instructions on where to sign in, see Sign in to Outlook.com or Outlook on the web.
Choose Settings next to your name in the upper-right corner of the page, then click Options.
In the left navigation bar, under General, choose Mobile Devices.
Select your phone in the list, and then select Remove to delete the device partnership.
Select Yes in the confirmation box.
If you only want to remove this device from the list, stop here. If you're attempting to fix a sync issue, continue with the remaining steps below.
Go to your mobile device and power it off completely.
Restart your mobile device after a few seconds, and then sync your mailbox again.
Still need help?
Get help with Outlook.com:
Get help with Outlook on the web for business:
If you're using Office 365 operated by 21Vianet in China, see Contact Office 365 for business support - Admin Help.