[noAnswer]

I know of a company that missed its yearly Microsoft Exchange Online payment. After four month Microsoft cut of their email. Which one could argue is also a "public notice" because emails bounced. (That did the trick and the company paid immediately.)

You are telling me:

1. Microsoft should have tried to find a different way to contact and reach out.

2. That you would have moved your eMail/Groupware to someone else because of that.

To each their own.

[Symbiote]

A sales person from Microsoft emails us every 3-6 months or so trying to upsell us on a more expensive 365 subscription.

I think their time would be well spent contacting a customer who hasn't paid.

Blocking sending email would also be a more reasonable step before blocking receiving email.

And yes, I'd consider moving.