Outlook 2016 continually prompts for login credentials issue

for Microsoft 365

Information updated on 22/05/2017 at 14:20 (GMT+9)

Issue: Regardless of checking the option to save the credentials information on Outlook, the login window keeps on prompting up continually for login credentials.

The issue has occurred mostly for customer who has set only IP restriction for application access. As a temporary solution, admin can remove IP restriction to allow users to access for the meantime. As of a permanent solution, there are two ways that can be done as followed:

  1. Allow by specifying User Agent (uastr:"%Outlook/16%").
  2. Allow by specifying Communication Method (ms_client_app:Microsoft.Exchange.Rest)

Please modify the setting on HENNGE Access Control (Access Policy Group) as shown below.

[Condition to allow Desktop/Mobile application access]

Edit to (Pattern 1):
ip4: or uastr:"%Outlook/16%"
Edit to (Pattern 2):
ip4: or ms_client_app:Microsoft.Exchange.Rest

If you have any question or concern, please contact directly to our Support Team for assistance.

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