I'm not sure I fully understand. You posted a link about Microsoft 365 no longer supporting Basic Authentication and then you talk about using our email service for notifications. Maybe I am missing the connection.

The Managed Backup notification feature supports using our servers, using Amazon SES, or using your own SMTP server. Many customers opt to use their own servers - we support SSL and full authentication.

More about notification options here in help:
https://mspbackups.com/AP/Help/settings/email-service

But in case I am misunderstanding, please restate the question.

Thanks.

Sorry for the confusion. I attempted to switch back to using MSP360 SMTP service however the user interface won't permit me to verify my sender email. I've read that other users have had issues switching back from custom SMTP. I have an open ticket for this issue.

For SPAM related reasons (SPF record etc) I prefer to run the notification over our own SMTP server. Turns out I may have read the article wrong. It appears as though they are not disabling Basic Authentication for SMTP.

"Today, we are announcing that, effective October 1, 2022, we will begin to permanently disable Basic Auth in all tenants, regardless of usage, with the exception of SMTP Auth."