Troubleshooting 'Error sending message. MS365 returned status 404: Resource could not be discovered.'

Microsoft 365 users on a Windows 10 device may encounter this error when emailing out of Acctivate: "Error sending message. MS365 returned status 404: Resource could not be discovered. " Try the following steps for a solution.

When emailing in Acctivate, Microsoft 365 users may encounter the below error or a similar message: 

Error sending message. MS365 returned status 404: Resource could not be discovered. 

Cause of the Problem:

This message may indicate your Microsoft 365 log in was unsuccessful or your authentication token has expired or been revoked. When attempting to connect or re-connect Microsoft 365 Mail in Acctivate, you may run into issues if your computer's default browser is set to Internet Explorer. This is because the OAuth2 redirect page does not work with Internet Explorer as official support for Internet Explorer has ended. 

Solution:

Ensure your computer's default browser is NOT set to Internet Explorer. To change your default browser in Windows

  1. Select the Start  button, and then type Default apps.

  2. In the search results, select Default apps.

  3. Under Web browser, if the browser currently listed is Internet Explorer, select another browser such as Microsoft Edge or Google Chrome. 

In Acctivate

  1. Open Configuration Management, File>Configuration Management. An Admin user must be available during this integration process for non-admin users. This Admin user user will need to open Configuration Management and allow the user to login to their Microsoft 356 Mail account when prompted.
  2. Select User>User Information and locate your Acctivate user ID
  3. Scroll to the bottom of the User ID information and click the "Disconnect" button in the email settings.
  4. Then you may re-connect your Microsoft Mail account as usual. Please follow the steps in this article for instructions on how to do so: Connect Microsoft 365 Mail in Acctivate