SMTP
552 Exceeded Storage
The requested mail action was aborted because the recipient's mailbox has exceeded its storage allocation. Unlike the temporary 452, this is a permanent rejection for this specific mailbox.
When You See This Code
When the recipient's mailbox is completely full and cannot accept any more messages. The recipient needs to delete old emails or increase their quota.
How to Fix
Notify the recipient through another channel that their mailbox is full. If you are the recipient, delete old messages or contact your mail administrator to increase the storage quota.