550 5.1.90 NDR

Iron Contributor

Problem: NDR "Remote Server returned '550 5.1.90 Your message can't be sent because you've reached your daily limit for message recipients."

Question 1: the code 550 5.1.90 doesn't exist under code description - can MSFT fix it? https://docs.microsoft.com/en-us/exchange/mail-flow-best-practices/non-delivery-reports-in-exchange-...

Question 2: There are two recipient limits - Recipient rate limit & Recipient limit. Which one has been exeeded in case of 550 5.1.90?

Question 3: How to find in Exchange Online / M365 Security a report that shows all NDRs for a domain? 

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