Situation: when the client setup Synology SNA notification using Office 365 account, they receive 535 5.7.3 authentication unsuccessful.
Troubleshooting: 1. Make sure you use correct SMTP server info:
Server: outlook.office365.com
Port: 993
Encryption: SSL/TLS
or
Server: smtp.office365.com
Port: 587
Encryption: STARTTLS
2. Make sure account credential are correct.
3. When filling out the Username, put in the full email address.
4. In out case, we fix the problem by switching Service Provider from SMTP Server to Outlook. Please refer to thispost:
