Sending email using Smtp.mail.microsoftonline.com

Question

The context:

We’re a small company that does not have an Exchange Server (or anyone dedicated to it) yet we still need to have/send emails.

Answer 1

Be sure to double check that your username is correct. It is not necessarily the same as your from email address. For example the from address may be "no-reply@yourdomain.com" but the username could be "mail-svc@yourdomain.onmicrosoft.com" depending no your setup and integration with Azure Active Directory etc.