Authentication Unsuccessful for Outlook 365

Problem/Motivation

Our mail server changed to Office 365, and I'm having trouble getting our new account, password reset, and webform email notifications to work. I checked Microsoft Office 365 documentation on the email server name (smtp.office365.com) and port (587), and updated the SMTP Authentication module with that information. The Office 365 account has a full license and has permissions to use SMTP. The username and password for the SMTP Authentication are correct. The "Email Options" Email From Address is different, as we want the emails to go to a distribution list. Use SSL is selected and TLS is on. This is how it was set up when we used the previous email server. Only server name and port changed.

This is the error code: 535 5.7.139 Authentication unsuccessful, the request did not meet the criteria to be authenticated successfully. Contact your administrator.

I changed the Basic Site Settings email address to match the SMTP email, but that didn't work. Then, I changed the Email From in SMTP Authentication to the same email, also didn't work. Still getting the "Unable to send email. Contact the site administrator if the problem persists."

Our Drupal support developer said to contact Microsoft, which I did, and they had me disable Security Defaults and ensure MFA wasn't enabled. I did both, neither fixed the issue.

The error persists, for example, in recent log messages:

smtp: Error sending e-mail from admin@domain.org to admin@domain.org: SMTP Error: Could not connect to SMTP host. Failed to connect to serverSMTP server error: Failed to connect to server

mail: Error sending email (from Site Name < admin@domain.org > to admin@domain.org with reply-to Site Name < admin@juvenilecompact.org >).

I'm the site admin and have access to Outlook365 as admin, as well, but I'm not a developer. Any help is appreciated.

I reviewed this article: https://www.drupal.org/project/smtp/issues/2365933 → which is what prompted me to try changing the Site Information email address, but that didn't resolve the issue.

Thanks