Can't connect to IMAP email account with New Outlook

Symptoms

When using the "New" Outlook desktop client, attempting to sign in to your email account gives errors similar to the following:

CONFIG_TEXT: "Something went wrong. Try again. You may need an app password."

CONFIG_TEXT: "Something went wrong with this account setup. Try again or use a different account."

Using the Troubleshooting button shows diagnostic information similar to the following as well:

CONFIG_TEXT: {"SessionId":"06c09a9e-cdea-9b46-XXXX-XXXXXXXXXXXX","Timestamp":1774536342644,"Error":"INVALIDCREDENTIALS INTERACTIONREQUIRED"}

CONFIG_TEXT: {"SessionId":"06c09a9e-cdea-9b46-XXXX-XXXXXXXXXXXX","Timestamp":1774536342644,"Error":"UNKNOWN undefined"}

This continues even after resetting the password and confirming it works via alternate methods.

Cause

The "New" Outlook desktop client no longer performs a direct IMAP connection to your server, and instead connects to Microsoft servers via a Cloud Account. If the associated email account has been used on another server, this Cloud Account managed by Microsoft may prevent the account from using the correct server.

To determine if this is the case, the "New" Outlook application will need to be started with its debug mode enabled so verbose errors are given. 

To launch debug mode:

1. On your local desktop: Press Windows key + R or Start > Command Prompt

2. Enter the following:

   # olk.exe --devtools

   This will launch the "New" Outlook application with developer tools enabled.

3. Access the Network tab in the developer tools window.
4. Set up your email account New Outlook, ensure to use the "Advanced" options to define IMAP ports and the correct mail server until the error occurs.
5. Check the developer tool window: connections will be listed on the left side, and any errors will be shown in red. Click on any of these connections for more details.

6. On one of the error connections, click on the Response tab to see the full error message provided by Microsoft. For example:

   CONFIG_TEXT: {
    "idpStatusCode": "BadRequest",
    "error": "BadRequest",
    "errorDescription": "Changing the ImapRemoteServerInfo is not allowed. Attempted to changed it from 'mail.example.tld' to 'newmail.example.tld",
    "innerError": null
   }

   This particular error means that there exists an account within Microsoft's systems, such as a previously set up IMAP Cloud account, that when it was created used a different IMAP server. Due to Microsoft's security policies on these accounts this information cannot be changed.

Resolution

1. Use Classic Outlook, or an alternate desktop email client that still performs direct IMAP connections.
2. Try to remove the affected email address from on all devices still configured with the old mx.domain.tld server
3. Contact Microsoft to delete any references/accounts for user@domain.tld within their systems.