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How to Fix Outlook.com IMAP Migration Authentication Errors
Question details
The user is attempting to migrate emails from Outlook.com to Microsoft 365 but is encountering authentication failures despite successful endpoint connection tests.
- Product
- Microsoft 365 / Outlook.com
- Device & OS
- not provided
- Scenario
- Setting up an IMAP migration batch in the Microsoft 365 admin center to import emails from an Outlook.com account.
- Observed behavior
- The migration fails with an ImapAuthenticationException stating the username or password is incorrect, or IMAP access is disabled, even though Test-MigrationServerAvailability is successful.
Verify that you have full access to both the source Outlook.com account security settings and the destination Microsoft 365 Exchange admin center.
Generate and Use an App Password for Outlook.com
Standard passwords often fail during IMAP migrations if the source account has modern security enabled. Generating an App Password bypasses this legacy authentication block.
Microsoft accounts with Two-Step Verification enabled will actively reject standard account passwords during legacy IMAP syncs or migrations. To successfully authenticate the migration batch, you must create a dedicated App Password.
Sign in to the Microsoft account security dashboard (account.microsoft.com/security) using the credentials of the Outlook.com account you are trying to migrate.
Navigate to 'Advanced security options'. If Two-Step Verification is not already turned on, enable it. App passwords cannot be generated without this feature.
Scroll down to the 'App passwords' section and click 'Create a new app password'. A 16-character password will be displayed on the screen.
Go to the Microsoft 365 Exchange admin center. Update your migration endpoint or migration batch CSV file, replacing the standard Outlook.com password with the newly generated 16-character App Password.
Escalate to Microsoft Exchange Support
If credentials are correct and app passwords still fail, the issue may stem from tenant-level blocks or backend Exchange server issues that require direct Microsoft support.
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Frequently Asked Questions
Why does Test-MigrationServerAvailability succeed if the migration fails?
The Test-MigrationServerAvailability command primarily checks network connectivity and ensures the IMAP server is reachable on the specified port. It does not fully validate the account-specific credentials or bypass modern authentication policies that block the actual data sync.
Does Outlook.com support legacy IMAP authentication?
Outlook.com is phasing out basic/legacy authentication in favor of modern authentication (OAuth2). However, for older IMAP migration tools, using an App Password is currently the standard workaround if Two-Step Verification is enabled.
Where can I check if IMAP is disabled on my Outlook.com account?
Log in to Outlook.com via a web browser, click the Gear icon (Settings), navigate to Mail > Sync email, and look for the 'POP and IMAP' section. Ensure that external apps and devices are allowed to connect.
