SMTP 452: insufficient system storage or too many recipients
The receiving server can't accept the message right now because of a storage limit, or because the message has more recipients than it takes in one go.
452 4.5.3 Your message has too many recipients.
Start of Gmail's text for this case, as listed in Google's SMTP errors reference.
What 452 means
RFC 5321 defines 452 as "Requested action not taken: insufficient system storage". It is temporary: the condition may clear, so the sender retries.
The same code covers too many recipients. RFC 5321 explains that RFC 821 listed the "too many recipients" error as 552 by mistake and that the correct reply is 452. A conforming server already has at least 100 recipients buffered when it sends this reply, and the sending server is expected to deliver the rest in another transaction. Gmail returns 452 4.5.3 for too many recipients, and 452 4.2.2 when a recipient's inbox is out of storage space.
So a 452 has three likely meanings: the server's disk is full, the recipient's mailbox is full, or your message had too many recipients for one transaction. The enhanced code tells you which: in the IANA registry, X.2.2 is "Mailbox full", X.5.3 is "Too many recipients" and X.3.1 is "Mail system full".
Likely causes
- The recipient's mailbox is over its storage quota.
- The message lists more recipients than the server accepts in one transaction.
- The receiving server is low on disk space.
How to fix it
If you sent the message
- For too many recipients: let your server split the delivery, or send to smaller groups or a mailing list.
- For a full mailbox: wait, or contact the recipient another way so they can clear space.
If you're the recipient or their admin
- Delete or archive mail to get back under your quota, or ask your admin for more storage.
- If your server sends 452 to everyone, check free disk space on the mail store and queue.
Frequently asked questions
Why did I get 452 for too many recipients and not 552?
RFC 5321 says 452 is the correct code for too many recipients, because the sender can deliver the remaining recipients in another transaction. Some older servers still send 552 for this, and RFC 5321 tells clients to treat that 552 as temporary.
Does a 452 mean the recipient's mailbox is full?
Sometimes. Gmail uses 452 4.2.2 when the recipient's inbox is out of storage. Other 452 replies mean too many recipients or a full server disk, so check the enhanced code and text.
Sources
- RFC 5321: Simple Mail Transfer Protocol (reply codes, section 4.2)
- RFC 5321, section 4.5.3.1.10: Too many recipients code
- IANA: SMTP Enhanced Status Codes registry
- Gmail SMTP errors and codes (Google Workspace Admin Help)
Provider messages are quoted as the provider publishes them. Servers can change their wording, so the bounce you received may differ slightly.
Related codes
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