If you are having issues with your account being locked, having a device with an old password, or even having an old device still linked, could be the reason that you are being locked out. In this case you should update your password on your phone. If you have lost the phone and wish to remove the access to your email this tutorial will show you how to do that using O365 Outlook.
The first step is to navigate to Outlook from your browser of choice. Next in the top right hand corner of the screen you will see a gear symbol to indicate the settings. Click on it and it will open.
Step 2: Once opened, you may search for “manage mobile devices”
It will come up as the first result.
Step 3: Click on the result
Here you should see all the connected devices that you have synced to your email. You want to place your cursor on the device that you wish to remove and click on the trash symbol to delete.The symbol will only appear when your cursor is on the device.
Then you are all set, you have successfully removed the device and should no longer see it in your list of phones.