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Troubleshooting: Delenta SMTP Integration with O365

How to Resolve Authentication Errors When Connecting Microsoft Exchange & Entra to Delenta

Renaud Bonavie avatar
Written by Renaud Bonavie
Updated over a month ago

If you're encountering a general authentication error stating that access is "blocked or not allowed," it's likely due to security settings in your Microsoft Exchange and Microsoft Entra (formerly Azure AD) that are not compatible with Delenta's current authentication method.

Why Is This Happening?

Delenta currently relies on legacy SMTP authentication, which requires specific configurations that may not be enabled by default in Microsoft 365 environments.

What Needs to Be Enabled?

To successfully connect your mailbox with Delenta, ensure the following:

  1. SMTP Authentication Must Be Enabled

    • By default, SMTP Auth is disabled on new Microsoft 365 (M365) installations.

    • You need to manually enable SMTP Auth for the mailbox you intend to use with Delenta.

  2. Legacy Authentication Must Be Allowed

    • Microsoft Entra enforces modern authentication by default, blocking legacy authentication methods for security reasons.

    • To use Delenta, you need to allow legacy authentication for the mailbox.

You can check SMTP Auth by following these steps.

Recommended Approach

Since security defaults cannot be targeted per user, turning them off would affect all users in your organization. Instead, it’s recommended to:

  1. Switch to Conditional Access Policies

    • Security defaults apply organization-wide, but Conditional Access allows user-specific exceptions.

  2. Exclude the Specific User from Login Restrictions

    • On the user account you wish to use for Delenta email sending, remove all Conditional Access policies related to login requirements, such as MFA.

  3. Save Changes and Test Again

    • Once these settings are updated and saved, try connecting Delenta again—it should work at this point.

By making these adjustments, you can ensure a smooth email integration with Delenta while maintaining overall security for your organization.

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