SMTP 551 User Not Local vs 552 Exceeded Storage
Both SMTP 551 (User Not Local) and 552 (Exceeded Storage) belong to the 5xx Permanent Negative category. 551 indicates that the recipient is not local to this server and the server does not accept mail for forwarding. Unlike 251, this is a rejection — the server will not relay the message. Meanwhile, 552 means that 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.
Description
The recipient is not local to this server and the server does not accept mail for forwarding. Unlike 251, this is a rejection — the server will not relay the message.
When You See It
When sending to a recipient that has moved or whose mailbox is hosted elsewhere, and this server refuses to forward the message to the new location.
How to Fix
Check the server's response for a forwarding address and resend directly to that address. Update your contact records if the recipient has permanently moved to a new mail server.
Description
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 It
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.
Key Differences
SMTP 551: The recipient is not local to this server and the server does not accept mail for forwarding. Unlike 251, this is a rejection — the server will not relay the message.
SMTP 552: 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.
You encounter 551 when when sending to a recipient that has moved or whose mailbox is hosted elsewhere, and this server refuses to forward the message to the new location.
You encounter 552 when 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.
When to Use Which
For 551 (User Not Local): Check the server's response for a forwarding address and resend directly to that address. Update your contact records if the recipient has permanently moved to a new mail server. For 552 (Exceeded Storage): 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.