Good afternoon

I'm from a Belgian company which sends about 2 million mails per day.
On the end of april and beginning of march we suddenly received a lot of hard bounces on Microsoft accounts. This all happened on a very short period. We tested a sample of these mails by sending from a private account and we also received a hard bounce response.

We think Microsoft closed a lot of unused accounts but we find no info online. Did anyone else experience this?

Looking forward to feedback.

Kind regards