The problem is that the person asking the question is only looking at things from their own perspective. They didn't change anything, so of course nothing changed. This point of view is inherently self-centered, thinking that the only thing that matters is the sender. It demonstrates a failure to understand one of the core concepts of SMTP. Each side of a SMTP transaction pays for email.
Microsoft is introducing new limits for onmicrosoft.com domains. Organizations can now send a maximum of 100 external emails per day via these standard domains to prevent spam. The new measure limits messages from onmicrosoft.com domains to 100 external recipients within 24 hours. Previously, there were no limits for Microsoft Online Email Routing Address (MOERA) domains. Microsoft is responding to an ongoing issue within Microsoft 365. Spammers are abusing new tenants to send large amounts of unwanted emails before Microsoft can intervene.