eM Client for Mac 8.0.2958 Office 365 Modern Auth

I cannot add an Office 365 Account using Modern Auth. There was a workaround in the Windows Client by adding a registry key which would enable the Modern Auth window to appear. This would allow you to input your Office 365 credentials. I cannot for the life of me find any related information for the Mac version.

Found the information… Hope this helps other people as well. I believe this would fix the endless password loop for Office 365 accounts.

eM Client for Windows

  • Download the attached registry file in this article.
  • Run it while eM Client is still closed and confirm the changes it will make.
  • Run eM Client and use the automatic setup to set up your accounts with oAuth.

If you’d like to add the needed registry key manually instead of using our provided file:

  • Run Regedit
  • Go to Computer\HKEY_CURRENT_USER\Software\eM Client
  • Add the key AllowExchangeOnlineOAuth and set its value to 1
  • Then run eM Client and use the automatic setup to set up your accounts with oAuth.

eM Client for MacOS

  • Open the Terminal
  • Execute this command:
  • defaults write com.emclient.mail.client AllowExchangeOnlineOAuth -bool TRUE
  • Run eM Client and use the automatic setup to set up your accounts with oAuth.


Having downloaded em Client to test it with the company office 365 mailbox. The workaround with the registry entry (on a mac) does work to a certain degree so that it has a pop-up window asking for the password and the 2nd factor. However, after both have successfully been entered the windows seems to be in a loop and is constantly trying to log in. In addition to that another window pops up asking which application should be opened for com.emclient.mailclient://oauth/? - with different hashes after the question mark.

This does not stop until i close the password and 2fa window which results in the account setup process being aborted. When checking the microsoft page with my applications i see that em client is authorized. Looks like the authorization never gets through to em client!?

Please let me know if there is anything i can do to get this working to allow me to test em Client.


I have exactly the same problem. I am using emClient 8.1.1083 (c197f89) on MacOS Big Sur (11.2.1). I used terminal to edit the defaults for emClient, but I am stuck in a never ending loop of authentication window which eventually leads to an error and I have to abort. This is really upsetting – how can it be that v8 of this client is shipping and something like this cannot be solved? Makes me very reluctant to pay for it.