Hello Maxi_Mustermann, If you've enabled IMAP for the user in the Office 365 admin console and created an authentication policy allowing basic authentication for IMAP using Exchange Online PowerShell, and Multifactor Authentication (MFA) is disabled for the user, yet you're still facing issues, here are some additional steps you can take to troubleshoot:
1. **Check IMAP Status:**
- Confirm that IMAP is enabled for the specific user in the admin console. Navigate to the user's mailbox settings and ensure that IMAP is enabled.
2. **Verify Authentication Policy:**
- Double-check the authentication policy settings using the following command:
```powershell
Get-AuthenticationPolicy -Identity "Allow Basic Auth for some ancient application" | Select-Object AllowBasicAuthImap
```
Ensure that the `AllowBasicAuthImap` property is set to `$true`.
3. **Test IMAP Connection:**
- Use a third-party mail client (e.g., Outlook, Thunderbird) to test the IMAP connection. Manually configure the IMAP settings with the user's Office 365 credentials.
4. **Check IMAP Logs:**
- If possible, check IMAP logs on your email client for any error messages or connection issues.
5. **Review Exchange Online Logs:**
- Review logs in the Exchange Online admin center for any errors related to IMAP connectivity.
6. **Verify Network Settings:**
- Ensure that there are no network restrictions preventing IMAP traffic to Office 365. Check firewalls, proxies, or any other network devices that might be involved.
7. **Review Microsoft 365 Service Health:**
- Check the Microsoft 365 Service Health Dashboard for any ongoing issues related to IMAP connectivity. There might be service incidents impacting your region.
8. **Check Client-Specific Requirements:**
- Different email clients may have specific requirements or settings for IMAP connectivity. Review the documentation or support resources for the client you are using.
If the issue persists after going through these steps, you may want to contact Microsoft Support for further assistance. They can provide more in-depth troubleshooting and address specific issues related to your Office 365 environment.
Have a great day Maxi_Mustermann
