SMTP Authentication Error in osTicket

DanielvG

Hello,

I am encountering an issue with SMTP authentication in osTicket. I have a service account that has access to a few other shared mailboxes in MS365. While IMAP authentication works correctly and is able to fetch mail, SMTP authentication fails with the error:

5.7.3 Authentication unsuccessful [AS4P190CA0027.EURP190.PROD.OUTLOOK.COM 2025-01-10T12:39:41.164Z 08DD3131E49799A4]

System Information:
osTicket v1.18.1 (0375576)
Web Server nginx/1.18.0
MySQL 8.0.40
PHP 8.3.15

Steps Taken:

Configured SMTP settings in osTicket as follows:
SMTP Server: outlook.office365.com
Port: 587
Authentication: Same as External Mailbox
Verified that the service account has the necessary permissions:
Send As
Read and Manage
Followed the osTicket Microsoft Authorization Guide for configuration. OAuth setup and Shared Mailbox

Despite these steps, the SMTP authentication error persists. I have also reviewed similar issues on the osTicket forum, such as this thread, but the problem remains unresolved.

Could anyone provide guidance or suggest additional steps to resolve this issue?

Thank you for your assistance.

KevinTheJedi

DanielvG

Sounds like Authenticated SMTP is disabled for the account in Microsoft.

Cheers.

DanielvG

Hi,

Thank you for your suggestion. However, Authenticated SMTP is already enabled for the account in Microsoft 365. I’ve double-checked this in the Admin Center under Active Users > Email apps. Despite this, the SMTP authentication issue persists.

Do you have any other suggestions or things I could try to resolve this?

Thanks in advance!

KevinTheJedi

DanielvG

You gave the user Read and Manage and Send As permissions for the mailbox?

Cheers.