Outlook for MAC login prompt

Copper Contributor



I was recently migrating a customer from Syndication to CSP account(They didn´t wanna wait for MS migration and wanted to change their default domain). Everything went smooth and they are up and running as it suppose to.


The only problem that remains are 2 user which are facing the login prompt for Office 365 everytime they start Outlook. Other Office apps are working as a charm and Outlook are working aswell except the login prompt.


It´s the modern UI that pop ups and i´ve checked for modern authentication but it´s turned off on the tenant.

I´ve asked the customer to try the Outlook assistant tool to troubleshoot and also asked the customer to delete every entry that has to do with Office 365 and ADAL in keychain... I´m not certain that this things has helped but i need some more advice regarding this issue.


Do anyone of you know what we can do about this?

BR Martin Front

7 Replies

It seems like a clear of keychain works.

After a couple of restarts it seem to work as it should.


I´ll update this post on Thursday if the problem are solved!

best response confirmed by Martin Front (Copper Contributor)

Microsoft working on a fix as soon as tehy can!

In the meanwhile I have a workaround which should help you.

1. Go to KeyChain Access

2. Search "Exchange" under Login --> All Items and delete everything

3. Search "Office" and delete everything

4. Search "ADAL" and delete everything

5. Launch Outlook

6. You will get the activation prompt and then If account is already added you will see the password prompt for app and ADAL again.

Please do 2-Factor Authentication if asked to and you should be able to login. After this on each launch you will not face the issue temporarily.

This is not a permanent fix but will help for a little bit.


This workauround works. The customer tried this in Monday and it works for them now!


Thanks for the detailed guide for other people if they experience this issue!


This worked for me.

We are starting to see this a lot since the return of everyone from holiday.

I have well over 800 users using outlook for mac 2016. 

Deleting the keychain entries mentioned resolves the issue but the call volume for the problem is increasing.

Is anyone aware of what changed to cause the issue? 

Window server 2012 r2 ADFS



It just started for me the past several days, where I could not login to Outlook (mac client) at all. It had never happened before. I am not sure what caused it .

Hello @Martin Front 

We're facing the same issue and we would like to fix the bug. 

I inform you our users are on Office Pro Plus 16.29 & it's a last the recent version but they're prompting many times to enter the password for Outlook 

Could you help us to find a solution 


Thank you,