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.

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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.


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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.

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I am having this exact same issue. Terminal command seemed to work (OAuth dialog box appears), but after I enter the 2FA it gets stuck in an infinite loop.

One thing I noticed is that if I try to set up using “Exchange” instead of auto, it cannot find the configuration server. But, if I copy and paste the URL from Outlook (where my account is set up), it gets further along (but ultimately still does not work). I don’t know if this is related, but there doesn’t seem to be an option to manually specify the server address.

I have been using eM client for a month (before my organization switched servers) and I greatly preferred it over Outlook. Now I am unable to use it at all!

eM client 8.1.1083 (c197f89)
macOS 10.15.7

I tried eM Cleint with Office 365 and had no problems connecting WITHOUT registry hacks or terminal commands.

Can you remove your Office 365 account from eM Client, and undo any registry hacks or commands, then update to the latest version in the Release History. Once the install is complete, add your Office 365 account again and see what happens.

Depending on what versio9n you are currently using, and if you may want to revert to that version after this test, make a backup using Menu > Backup before you upgrade.

Sometimes users have an issue with oAuth because they do not have a default browser selected in the OS. So if you do not see the complete oAuth popups, try changing your default browser, then do it again.

Hi Gary,

I had already tried removing and reinstalling eM client and was using the latest version. Per your suggestion, I tried switching my default browser from Chrome to Safari, but it did not help.

While the infinite loop is in progress, the New Account window says “Obtaining server configuration records.” As with afaerber, I can verify through office.com that the authorization of eM client appears to be successful-- but the client still does not work.

Thanks for your help.

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FWIW, it does not appear that eM client uninstalls completely. I tried to uninstall the latest version and install 7.xx, but when I go to open eM client it says “The application cannot start because the database on this computer was modified by a newer version of this application.”

It’s not clear how to remove the software entirely, there is no trace of the other version in ~/Applications or ~/Library/Preferences

When you uninstall the application, you should be asked if you want to delete the database directory. If you choose not to delete it, you will not be able to launch an older version of eM Client, as the data in that folder (emails, settings etc.) is not backwards compatible.

In Windows that folder is C:\Users\yourusername\AppData\Roaming\eM Client. You can rename or delete it manually to allow you to launch an older version of eM Client.

I am not sure what the location is for Mac, but if you still have the latest version of eM Client installed, you can find the location in Menu > Settings > General > Storage.

Thanks Gary. As per moralesa (original post), this is a macOS specific issue.

I was able to get 7.xx installed by deleting additional files in ~/Library/Application Support/ (there is no “uninstall” application – as with most macOS applications, uninstalls are done by simply deleting the .app folder). However, 7.xx did not fix the issue.

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The OP neglected to mention that when using the terminal command or registry hack work-around, you should make sure to disable the ‘Offline Address Book’ service during the last step of the setup. That is because it is not compatible with the oAuth setup and, according to eM Client, could cause additional problems.

Hmm, is there any way to proactively disable ‘Offline Address Book’ prior to setting up my account? Because it never gets to that ‘last step’, and I never see any options related to it.

I am not sure.

It is a pity you did not get as far as purchasing a Pro License, as this is something you would need eM Client Support to help with.

Thanks for your help anyway