Duo Access Gateway login loop with Outlook


Has anyone else experienced a login loop with the DAG (Duo Access Gateway) and the Outlook client.
we seem to think its related to the Microsoft OS build (1709). After 2FA our Office 365 environment, we have run into a few things regarding how our Click-To-Run Office Applications including Skype for Business… will prompt the user over and over again the DAG login window even after entering the correct credentials.


Are you running a hybrid installation of Office 365 and On-Prem? If so, you need to make sure modern auth is enabled on premise as well as in O365. If you are not enabled for modern auth on-prem, you will continually get prompted for anyone that opens anything on premise.

We recently ran into this problem and found modern auth was not fully working on premise. To check a user, ctrl-right click the Outlook icon in the task bar and choose “Connection Status…”. If you do not see Bearer as the Authentication type for all connections, that is likely the cause.