An update to the Microsoft Outlook 2016 application released in October 2017 has caused it to repeatedly prompt certain users for their username and password information. Per Microsoft, this bug was introduced after updating to Current Channel build 16.0.8431.2079. Microsoft has not yet released a fix for this bug, but has provided a workaround to roll back to a prior version of the software build.
Do the following to revert to an earlier build:
Open a command prompt window.
At the command prompt, run the following commands:
cd %programfiles%\Common Files\Microsoft Shared\ClickToRun\officec2rclient.exe /update user updatetoversion=16.0.8326.2107
Note: If 16.0.8326.2107 is unavailable, refer to Version and build numbers of update channel releases to find another recent version for your respective channel.