Request to Enable SMTP Authentication for ClientCare Email Sending

Question

Hello Microsoft Support Team,

I need assistance enabling email sending from a third-party application called ClientCare. We are attempting to send emails from an Outlook/Microsoft account via SMTP but are encountering authentication errors.

Connection Details

• Email Account: ******@outlook.com

SMTP Server: smtp-mail.outlook.com

Port: 587

Security: TLS / STARTTLS enabled

Username: ******@outlook.com

The Issue

We have already created and tested an App Password, but the connection continues to fail. When ClientCare attempts a test email, the Microsoft server returns the following error:

5.7.139 Authentication unsuccessful, basic authentication is disabled.

This indicates that while ClientCare can reach the SMTP server, Microsoft is blocking the authentication method for this specific mailbox.

Request for Clarification

Could you please check this account and confirm the following:

If this is a Microsoft 365 Business mailbox: Please enable Authenticated SMTP for this user account.

If this is an Outlook.com Personal account: Please confirm if SMTP Basic Authentication (including App Passwords) can no longer be enabled. We need to know if this mailbox is still compatible with standard SMTP sending or if it now requires OAuth 2.0.

Reference Documentation:

Authenticated Client SMTP Submission

Modern Authentication Requirements

Thank you for your help.Hello Microsoft Support Team,

I need assistance enabling email sending from a third-party application called ClientCare. We are attempting to send emails from an Outlook/Microsoft account via SMTP but are encountering authentication errors.

Connection Details

Email Account: ******@outlook.com

SMTP Server: smtp-mail.outlook.com

Port: 587

Security: TLS / STARTTLS enabled

Username: ******@outlook.com

The Issue

We have already created and tested an App Password, but the connection continues to fail. When ClientCare attempts a test email, the Microsoft server returns the following error:

5.7.139 Authentication unsuccessful, basic authentication is disabled.

This indicates that while ClientCare can reach the SMTP server, Microsoft is blocking the authentication method for this specific mailbox.

Request for Clarification

Could you please check this account and confirm the following:

If this is a Microsoft 365 Business mailbox: Please enable Authenticated SMTP for this user account.

If this is an Outlook.com Personal account: Please confirm if SMTP Basic Authentication (including App Passwords) can no longer be enabled. We need to know if this mailbox is still compatible with standard SMTP sending or if it now requires OAuth 2.0.

Reference Documentation:

Authenticated Client SMTP Submission

Modern Authentication Requirements

Thank you for your help.

Answer 1

For Outlook.com personal mailboxes, POP, IMAP, and SMTP now require Modern Authentication (OAuth2). Basic authentication (username/password, including app passwords) is not supported for SMTP on Outlook.com.

From the documented settings for Outlook.com:

• SMTP server: smtp-mail.outlook.com
• Port: 587
• Encryption: STARTTLS
• Authentication Method: OAuth2/Modern Auth

Because the error returned is:

5.7.139 Authentication unsuccessful, basic authentication is disabled.

this is expected when attempting to use basic SMTP auth (even with an app password) against an Outlook.com account. The mailbox is still compatible with SMTP sending, but only with OAuth2/Modern Auth, not with basic authentication.

For this scenario:

• If the mailbox is an Outlook.com personal account, SMTP basic authentication cannot be enabled. The third‑party app must support OAuth2/Modern Auth for SMTP to work with Outlook.com.
• If using Microsoft 365/Office 365 business mailboxes instead, authenticated SMTP is supported but is being deprecated for basic auth; Modern authentication (OAuth) is recommended. SMTP AUTH can be enabled per mailbox in Exchange Online when using Microsoft 365 business accounts.

If the ClientCare application cannot use OAuth2/Modern Auth for SMTP, it will not be able to send mail directly using an Outlook.com personal mailbox with the documented, supported configuration.

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References:

• POP, IMAP, and SMTP settings for Outlook.com
• How to set up a multifunction device or application to send email using Microsoft 365 or Office 365
• Fix issues with printers, scanners, and LOB apps that send email using Microsoft 365
• Create credentials for Simple Mail Transfer Protocol (SMTP) authentication