OAuth 2.0 for Office 365 Accounts (installed applications)
Enabling SMTP Auth for Specific Mailboxes
Sending emails using Microsoft365 (Office365) - Powered by Kayako Help Desk Software
How can I restrict outgoing SMTP access to specific countries to limit SMTP auth brute force attacks using Juggernaut Firewall? - Tudásbázis - Danami
SMTP Authentication Unsuccessful 535 despite already being allowed - Microsoft Community