If you have an environment that is newly deploy or newly upgraded and after few months, than you have only encounter your Outlook frequently shows the pop-up for credentials. Thus, you have no idea, how come there would be such issue happen, even though you have deploy it with best practice.
To check what is causing this situation is to run wireshark;
- Run wireshark on a user’s computer, either connected to LAN or Internet.
- Close all necessary applications
- Open and run the wireshark
- Open Outlook only
- If no pop-up shown, than open other microsoft applications, such as excel or skype for business
- If than pop up shown, than stop and save your wireshark logs
- Analyse the wireshark logs
- You will probably see there is multiple re-transmission of the firewall connection, which successful and than fail instantly
- This could be your firewall issue that causes the pop up
- You can also check from Event viewer from the user’s computer, based on the similar steps for wireshark
For such situation happen, the only assumption you will ask yourself is;
- Has there be changes with firewall?
- Is the firewall having issue?
- Is my exchange or exchange hybrid having issue?
- Is my ADFS having problem? (You can check from portal access is it accessible, if yes than ADFS is not the problem)