Google Inbox “happy” hour
Delivery to the following recipient failed permanently:
inbox@google.com
The error that the other server returned was:
550-5.2.1 The user you are trying to contact is receiving mail at a rate that
550-5.2.1 prevents additional messages from being delivered. For more
550-5.2.1 information, please visit
550 5.2.1 http://support.google.com/mail/bin/answer.py?answer=6592 j9si8791583lab.13 - gsmtp In a big company such as Google with very complex systems, such a thing is likely to happen. Even with very detailed specification with rigid scrutiny, details like this will fall through the cracks. Often we anticipate every possible edge cases but haven't taken into account outside systems that plays a big role too, which leads to cases such as this.