5.5.1 Authentication Required - Outlook is receiving email but I'm unable to send email

5.5.1 Authentication Required - Outlook is receiving email but I'm unable to send email

I just tried sending out an email to my business contacts notifying them of my new email address and received the following:

Error: 5.5.1 Authentication Required.

Details: Cannot send mail. The SMTP server does not recognize any of the authentication methods supported by Outlook. Try changing the SMTP authentication options in Account settings or contact your network administrator.

Error Code: -17092

How do I resolve this? Thank you for your time!