About the phenomenon where you are asked to log in many times in Outlook 2016 3

for Microsoft 365

October 26, 2018, 10:00 AM

We have received inquiries from some customers who are experiencing repeated login prompts in Outlook 2016, regardless of credential persistence.

After investigating, we have identified a situation where authentication requests from HENNGE Access Control are reaching Microsoft's IP addresses in some communication methods of Exchange.

Customers experiencing this issue may be affected if they have set the "Conditions for allowing application access" in HENNGE Access Control to permit only internal IP addresses.

As a workaround, considering adding Microsoft's IP addresses to the permission conditions may improve the situation. Please review and consider the following steps:

● Configuration Location
HENNGE Access Control Management Screen > Access Policy Group > [Conditions for allowing access from applications (desktop/mobile)]

Example:
Before Change:
ip4:111.111.111.111

After Change:
ip4:111.111.111.111 or ip4:13.107.6.152/31 or ip4:13.107.9.152/31 or ip4:13.107.18.10/31 or ip4:13.107.19.10/31 or ip4:13.107.128.0/22 or ip4:23.103.160.0/20 or ip4:23.103.224.0/19 or ip4:40.96.0.0/13 or ip4:40.104.0.0/15 or ip4:52.96.0.0/14 or ip4:111.221.112.0/21 or ip4:131.253.33.215/32 or ip4:132.245.0.0/16 or ip4:134.170.68.0/23 or ip4:150.171.32.0/22 or ip4:157.56.232.0/21 or ip4:157.56.240.0/20 or ip4:191.232.96.0/19 or ip4:191.234.6.152/32 or ip4:191.234.140.0/22 or ip4:204.79.197.215/32 or ip4:206.191.224.0/19

※The above are the IP addresses publicly available as of October 25, 2018.
For the latest information, please refer to the details provided in Exchange Online ID1.
https://docs.microsoft.com/en-us/office365/enterprise/urls-and-ip-address-ranges