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:

  1. Configured SMTP settings in osTicket as follows:
    SMTP Server: outlook.office365.com
    Port: 587
    Authentication: Same as External Mailbox

  2. Verified that the service account has the necessary permissions:
    Send As
    Read and Manage

  3. 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 replied to this.

  • DanielvG

    Make sure you are using v1.18.1 or v1.17.5, install the latest build of OAuth2 plugin, go to the email auth config popup, make sure Strict Matching is disabled, go to the Token tab, delete the existing token, submit the popup, authenticate as the service account, and retest.

    Cheers.

      DanielvG

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

      Cheers.

        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!

          DanielvG

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

          Cheers.

            Yes, in MS365 I gave the Service Account user 'Read and Manage' and 'Send As' permissions on the shared mailboxes I want in osTicket.

            Cheers.

              DanielvG

              Hmm.. try smtp.office365.com instead. Also, review the logs on the Microsoft side to see if there is any indication of why the authentication is failing.

              Just to be 100% certain, when you were setting up the authentication you unchecked the box for Strict Matching right? Also, when it directed you to Microsoft to login you logged in as the Service Account right? Lastly, if the answer is yes to those questions, when you click Config and go to the Token tab the resource owner shows as the service account right?

              Cheers.

                19 days later

                Thanks for the suggestion! I have tried using smtp.office365.com and got the same error. I don't see any auth logs of the service user.

                To confirm:

                • Strict Matching is unchecked.
                • Login was done using the Service Account when redirected to Microsoft.

                I have notested that my token resource owner is the shared mailbox I want to mail with, not the service account. How do I proceed?

                Appreciate the help!

                  DanielvG

                  Make sure you are using v1.18.1 or v1.17.5, install the latest build of OAuth2 plugin, go to the email auth config popup, make sure Strict Matching is disabled, go to the Token tab, delete the existing token, submit the popup, authenticate as the service account, and retest.

                  Cheers.

                    Thanks, that did it! Downloaded the new phar file, extracted it to the folder and it worked!

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