Temporary — will retry
SMTP 452
insufficient system storage
SMTP 452 means the receiving server will not take the message right now because of a storage or quota limit. RFC 5321 defines it as "insufficient system storage", and the same code is used when a message has too many recipients. It is temporary, so the sender retries.
How it appears
452 Requested action not taken: insufficient system storage
452 4.3.1 Insufficient system storage
452 4.5.3 Error: too many recipients
What causes it
- The recipient's mailbox is over quota (often shown as 452 4.2.2).
- The receiving server is short of disk space.
- You sent more RCPT TO commands in one transaction than the server allows.
- A per-sender rate limit is expressed as a 452 by some servers.
How to fix it
In order — try the first one first.
- Let the retry run. A mailbox that is only briefly full will accept mail again.
- If the text mentions too many recipients, split the send into smaller batches per message.
- If a mailbox stays full for weeks, treat it as abandoned and remove it.
Common questions
- What does SMTP 452 mean?
- SMTP 452 means the receiving server will not take the message right now because of a storage or quota limit. RFC 5321 defines it as "insufficient system storage", and the same code is used when a message has too many recipients. It is temporary, so the sender retries.
- Should I retry a 452 error?
- Yes, and your sending server does it automatically. 452 is a temporary deferral, and legitimate mail usually arrives on a retry within minutes or hours. Only investigate if it persists across many retries.
- How do I fix SMTP 452?
- Let the retry run. A mailbox that is only briefly full will accept mail again.
Specific 452 replies
Last reviewed 2026-09-11