Fluent SMTP plug in

Question

I have set up and authenticated access for my Fluent SMTP for Microsoft email - How can I confirm in the Azura App Registration the app has permission to send emails and that the required access has been approved.

I am getting an unauthorized during my email Test

Answer 1

For FluentSMTP’s normal interactive Microsoft 365 OAuth connection, verify that the app registration has Microsoft Graph → Delegated permissions → Mail.Send, that consent is shown as granted, and that FluentSMTP sends from the mailbox used during authentication.

Verify the permission and consent

1. Open the Microsoft Entra admin center.
2. Go to Identity → Applications → App registrations.
3. Select the app whose Application (client) ID is configured in FluentSMTP.
4. Select API permissions.
5. Under Microsoft Graph, look for:

   	API	Permission	Type
   	Microsoft Graph	Mail.Send	Delegated

   Delegated Mail.Send means “send mail as a user.” Microsoft Graph lists it as the least-privileged permission for sending as the signed-in user. The permission itself does not inherently require administrator consent, although tenant consent policies can still require administrator approval.^1^
6. Check the Status column:
   • Granted for <tenant name>: consent was approved.
   • Pending, blank, or Not granted: consent has not completed.^2^

If Mail.Send is absent:

1. Select Add a permission.
2. Select Microsoft Graph.
3. Select Delegated permissions.
4. Search for and select Mail.Send.
5. Select Add permissions.

If your organization blocks user consent, an authorized administrator must select Grant admin consent for <tenant> and approve the request. Adding a permission to the registration does not by itself grant consent.^3^

Reconnect FluentSMTP

After changing permissions or consent:

1. In WordPress, open FluentSMTP → Settings and edit the Microsoft 365/Outlook connection.
2. Confirm its client ID and tenant information match the app registration checked above.
3. In the app registration, open Authentication and confirm the redirect URI exactly matches FluentSMTP’s callback URL. Redirect URIs must match exactly.^4^
4. Disconnect and authenticate the FluentSMTP connection again so it receives a new token containing the newly consented permission.
5. Sign in as the mailbox configured as the FluentSMTP From Email, save the connection, and repeat the email test.^5^

If the From address is another or shared mailbox

If FluentSMTP authenticates one user but sends from another user or shared mailbox, delegated Mail.Send alone is not sufficient. Add Microsoft Graph Delegated → Mail.Send.Shared, and grant the signed-in user either Send As or Send on Behalf permission for that mailbox in Microsoft 365/Exchange. Microsoft documents both requirements for user-token scenarios.^6^

If the sender should be the authenticated mailbox, remove the alternate From address instead of adding shared-mailbox permissions.

Do not substitute SMTP application permissions

SMTP.SendAsApp is for an app-only/client-credentials SMTP protocol implementation. That model also requires tenant admin consent and registration of the service principal in Exchange Online.^7^

Do not add it merely because the plugin contains “SMTP” in its name. Use it only if FluentSMTP is explicitly configured for app-only SMTP OAuth rather than its normal interactive Microsoft 365/Outlook connection.

If the test remains unauthorized after reconnecting, capture the complete FluentSMTP error details. In particular, note whether it is an Entra AADSTS... consent error, an HTTP 401, or an Exchange send-as error; those identify whether the remaining issue is token acquisition, token permissions, or mailbox delegation.

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References

1. Microsoft Graph permissions reference
2. Error AADSTS650056: Misconfigured application
3. Troubleshoot consent issues in Microsoft Entra ID
4. Admin consent on the Microsoft identity platform
5. Outlook or Office365 with FluentSMTP
6. Send Outlook messages from another user using the Outlook mail API ...
7. Authenticate an IMAP, POP or SMTP connection using OAuth