5.2.2 is a permanent SMTP reply meaning mailbox full or submission quota exceeded. If the bounce mentions a full mailbox or QuotaExceeded, the problem is on the recipient's side. If it says "Submission quota exceeded", the problem is on your side: Microsoft says the sender exceeded the recipient rate limit or the message rate limit, and that it can also mean the account was compromised.
What 5.2.2 means
If the bounce mentions a full mailbox or QuotaExceeded, the problem is on the recipient's side. If it says "Submission quota exceeded", the problem is on your side: Microsoft says the sender exceeded the recipient rate limit or the message rate limit, and that it can also mean the account was compromised.
Common causes
The recipient mailbox is full
Most commonThe person has used all their storage. Mail will bounce until they delete mail or get more space.
You hit Microsoft 365 sending limits
CommonMicrosoft 365 limits how many recipients and messages one mailbox can send per minute and per day.
A compromised account is sending spam
Less commonA sudden burst that hits the limit can mean someone else is using the account.
How to fix 5.2.2
- 1
Read which 5.2.2 you got
Mailbox full: contact the recipient another way or try later. Submission quota exceeded: the fix is on your side.
- 2
Stay under the sending limits
Spread sends over time, or send bulk mail through a sending service instead of a Microsoft 365 mailbox.
- 3
Check the account if the volume was unexpected
Look for unknown sent items, inbox rules and sign-ins, and secure the account.
Confirm your domain is set up correctly
Most delivery failures — permanent or temporary — trace back to authentication or reputation. Run a free EmailHealth check to confirm SPF, DKIM, DMARC, blacklist status, and TLS are all healthy for your sending domain. If you send in volume, free daily monitoring will alert you before a small issue becomes a flood of bounces.