Enhanced SMTP status code · RFC 3463 · IANA
5.2.122 Recipient's per hour message receive limit exceeded
The Microsoft 365 recipient got more messages per hour than allowed.
- Class: Permanent failure
Class 5: a permanent failure. Resending the same message will not help: something about the message, the sender or the destination must change (RFC 3463 §3.1).
- Subject: X.2 · Mailbox
Something about the recipient's mailbox; under the recipient's control.
How 5.2.122 appears at providers
The exact text from the provider's documentation, as you see it in the bounce, and what it means.
Microsoft 365 / Exchange Online
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5.2.122
Recipient's per hour message receive limit exceeded
The Microsoft 365 recipient got more messages per hour than allowed.
Have the whole error message?
Sources: RFC 5321 · RFC 3463 · RFC 3464 · IANA · Gmail · Microsoft 365 · read on 26 September 2026