Outlook Login Problem

Problem:
Outlook verlangt immer wieder die Login-Daten. Es gibt keine Fehlermeldung, es wird nur immer wieder das Login Prompt aufgerufen. Meist ist ein Exchange Account dahinter bei diesem Problem.

Lösung:

Outlook 2016 password prompt
The fix is to create the following Registry keys on affected machine:
Navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\x.0\Outlook\AutoDiscover (x.0 corresponds to the Outlook version: 16.0 = Outlook 2016)
For Outlook 2016 version 16.0.6741.2017 and later versions, please add the following
DWORD: ExcludeExplicitO365Endpoint
value 1
Edit (2018-01-15): looks like there can be more to fixing this.
Close all office programs
In command prompt (as administrator)
cd %programfiles%\Common Files\Microsoft Shared\ClickToRun
officec2rclient.exe /update user updatetoversion=16.0. 8625.2139 (November release, per TommyBoyCDN at https://social.technet.microsoft.com/Forums/en-US/76bcbc41-afb2-4789-9064-c1d18e1a122e/outlook-2016exchange-2010-keeps-prompting-for-credentials?forum=outlook)
Let this finish the office update/change
Open any office program and disable updates by going to File/Office Account, then click on Office Updates and disable them (Important, create a calendar entry for you to re-enable these in 30 days)
Close all office programs
Start-“netplwiz”
Advanced
Manage Passwords button
Windows Credentials
Delete anything under Generic credentials that relate to outlook or your mail accounts
Restart the computer
It works!
If it still doesn’t work, remove the shared exchange account from Outlook (because you have a shared mailbox, I guess? this worked for a client)
Control Panel
Mail
Remove the shared account (setting user@domain as the default account)
open Outlook with only the user@domain in Outlook
Close Outlook
Go back to mail, re-add the shared mailbox
Set it as default (if it was before)
Then reopen Outlook and test.

Quelle:
https://www.reddit.com/r/sysadmin/comments/7pk33j/outlook_2016_password_prompt/