🛠️ Fixing Authentication Issues with Microsoft 365 IMAP in Mailbird Next

If you're encountering authentication problems when using a Microsoft 365 account with the IMAP protocol in Mailbird Next, then this article will walk you through why this issue occurs and how you can fix it.

⚠️ Understanding the "Authentication Unsuccessful" Error

When Microsoft 365 accounts are set up using the IMAP server type, users may see an "Authentication Unsuccessful" error when trying to send emails.

This happens because SMTP authentication is disabled by default in Microsoft 365 for security reasons. Organizations must enable this setting explicitly to allow outgoing mail via IMAP.

🔒 Best Practice: We highly recommend using the Exchange protocol (available with our Premium plan) for Microsoft 365 accounts. It’s significantly more secure and stable than IMAP.

🔧 How to Fix the Issue

You can still use IMAP with Microsoft 365, but you'll need to enable Authenticated SMTP to resolve this error.

👤 Enable Authenticated SMTP for an Individual User

Only an Administrator can enable this setting via the Microsoft 365 Admin Center:

1. Go to Microsoft 365 Admin Center.

2. Click on Users > Active users.

3. Select the user who needs access.

4. Go to Mail > Manage email apps.

5. Enable Authenticated SMTP.

6. Click Save changes.

📌 Note for GoDaddy users: SMTP can only be enabled at the organization level via PowerShell. Access to the Microsoft 365 Admin Center will be restricted, but we will include instructions on what to do below.

🏢 Enableing Authenticated SMTP for the Entire Organization (via PowerShell)

If you're enabling the setting for the whole organization, follow these steps:

1. Install PowerShell for macOS.

2. Log in to your Microsoft 365 organization via PowerShell.

3. Run the following command: Set-TransportConfig -SmtpClientAuthenticationDisabled $false

4. Confirm success by running: Get-TransportConfig | Format-List SmtpClientAuthenticationDisabled

    

If you see: SmtpClientAuthenticationDisabled: False, this means that SMTP authentication is now enabled. ✅

📚 Additional Resources

For detailed Microsoft documentation, please take a look at the following article provided by Microsoft: Authenticated client SMTP submission in Exchange Online.

🙋 Need More Help?

If you have any questions about Microsoft 365 SMTP authentication in Mailbird Next, please reach out to us here. Our Customer Happiness team is always here to assist you.