emailgtw: "535 5.7.3 Authentication unsuccessful" error connecting to Office365

Products

• DX Unified Infrastructure Management (Nimsoft / UIM)
• CA Unified Infrastructure Management On-Premise (Nimsoft / UIM)
• CA Unified Infrastructure Management SaaS (Nimsoft / UIM)

Issue/Introduction

Unable to configure the emailgtw probe settings using an Office365 SMTP server.

"Test" option in emailgtw probe SMTP menu fails and produces the following error in the emailgtw.log:

emailgtw: EHLO %MachineNameOfemailgdtwProbe%.domain.com
emailgtw: 250-%<server>.office365.com% Hello [##.###.##.##]
emailgtw: 250-SIZE 157286400
emailgtw: 250-PIPELINING
emailgtw: 250-DSN
emailgtw: 250-ENHANCEDSTATUSCODES
emailgtw: 250-AUTH LOGIN XOAUTH2
emailgtw: 250-8BITMIME
emailgtw: 250-BINARYMIME
emailgtw: 250 CHUNKING
emailgtw: (cmd_test_smtp_login) smtp_open succeeded
emailgtw: AUTH LOGIN
emailgtw: 334 ##########
emailgtw: (test_login) getting username and password for host ##.###.##.##]
emailgtw: ######## - found match [ ##.###.##.##]
emailgtw: <suppressed>
emailgtw: 334 ##########
emailgtw: <suppressed>
emailgtw: 535 5.7.3 Authentication unsuccessful [%<server>.<domain>.outlook.com]

Environment

• DX UIM 20.4.* / 23.4.*
• emailgtw probe version 2.83
• Office365 SMTP server

Cause

This issue is associated with the authentication process to the Office365 managed by the Office365 Admin.

Resolution

Here are some helpful links to troubleshoot this problem:

 1. Use Telnet to verify SMTP communication outside of the emailgtw probe
     --> How to Use Telnet to Test SMTP Communication | Microsoft Learn

 2. See the following link with a solution for the "535 5.7.3" SMTP error:
     --> SMTP.office365.com Relay 535 5.7.3 authentication unsuccessful

Additional Information

Related KB: emailgtw: 535 5.7.3 Authentication unsuccessful after upgrading to v2.91 (broadcom.com)