550 5.7.233 means your Microsoft 365 organization passed its daily limit for sending to external recipients, so Exchange Online refused the message. Wait for the count to fall, then resend and spread large sends out. The person you wrote to has nothing to do with it.
The limit counts every external recipient across every mailbox in the tenant. One campaign in the morning can make a colleague's invoice bounce in the afternoon.
How to read the result
Microsoft's sentence reads close to "tenant exceeded its daily limit for sending email to external recipients". Check the exact code, because the neighbours in Microsoft's list of non-delivery reports in Exchange Online count different things:
5.7.232 is the same limit on a trial tenant.
5.7.236 limits mail sent from your onmicrosoft.com address. Add a custom domain and send from it.
5.1.90 and 5.2.2 are about one sender or one mailbox, and both can mean the account is compromised.
5.7.703 is not a limit: your own block list stopped a recipient.
What to do next
Pause the large send. Whatever is still queued adds to the count, and colleagues' external mail keeps bouncing until it falls.
Wait, then resend. Once the window has rolled, send the bounced messages again.
Spread big sends out. A send spread over several days counts against several windows instead of one.
Keep outreach apart from company mail. Cold outreach sits best on its own sending domains and mailboxes, so a busy campaign never spends the allowance your finance and support teams need.
An address that does not exist still counts as an external recipient, so it spends allowance and then bounces on top. Verifying a list before you send keeps those out.