SMTP 452 Insufficient Storage vs 553 Mailbox Name Invalid
SMTP 452 (Insufficient Storage) is a 4xx Transient Negative response, while 553 (Mailbox Name Invalid) is a 5xx Permanent Negative response. 452 indicates that the requested action was not taken because the server has insufficient system storage. The server cannot accept more mail until storage is freed. In contrast, 553 means that the requested action was not taken because the mailbox name is syntactically incorrect. The email address does not conform to the expected format.
Description
The requested action was not taken because the server has insufficient system storage. The server cannot accept more mail until storage is freed.
When You See It
When the mail server's disk is full or the recipient's mailbox has exceeded its storage quota. The server cannot store additional messages.
How to Fix
If you are the sender, retry later after the recipient frees up space. If you manage the server, clear disk space, increase quotas, or archive old messages.
Description
The requested action was not taken because the mailbox name is syntactically incorrect. The email address does not conform to the expected format.
When You See It
When the sender or recipient address contains invalid characters, improper formatting, or violates the server's naming conventions.
How to Fix
Check the email address format — ensure it follows the standard [email protected] pattern with valid characters. Remove any spaces, special characters, or encoding issues from the address.
Key Differences
452 is a 4xx Transient Negative response, while 553 is a 5xx Permanent Negative response.
SMTP 452: The requested action was not taken because the server has insufficient system storage. The server cannot accept more mail until storage is freed.
SMTP 553: The requested action was not taken because the mailbox name is syntactically incorrect. The email address does not conform to the expected format.
You encounter 452 when when the mail server's disk is full or the recipient's mailbox has exceeded its storage quota. The server cannot store additional messages.
You encounter 553 when when the sender or recipient address contains invalid characters, improper formatting, or violates the server's naming conventions.
When to Use Which
For 452 (Insufficient Storage): If you are the sender, retry later after the recipient frees up space. If you manage the server, clear disk space, increase quotas, or archive old messages. For 553 (Mailbox Name Invalid): Check the email address format — ensure it follows the standard [email protected] pattern with valid characters. Remove any spaces, special characters, or encoding issues from the address.