In this post, let’s have a look at the error message “5.2.121 – Recipient’s per hour message receive limit from specific sender exceeded.” that you get when working with Microsoft 365 Exchange Online.
These are the errors that you usually receive when there is a problem in delivering the email message that was sent by you. These errors are generated and sent by Office 365. This is usually alled as DSN which stands for delivery status notification or in simple words bounce messages.
NDR or Non-delivery report is one of the common type of message that you receive which indicates to the user that the email was not delivered.
5.2.121 – Recipient’s per hour message receive limit from specific sender exceeded.
The sender has exceeded the maximum number of messages they’re allowed to send per hour to a specific recipient in Exchange Online.
The automated mailer or sender should try again later, and reduce the number of messages they send per hour to a specific recipient.
This limit helps protect Microsoft 365 or Office 365 users from rapidly filling their inboxes with a large number of messages from errant automated notification systems or other single-sender mail storms.