Basic SMTP reply code · RFC 5321

452 Insufficient system storage

The action was not taken: the server does not have enough space right now.

Class: 4yz · Temporary failure
4yz: a transient failure. The command was not accepted, but may succeed if repeated; the sending server should try again (RFC 5321 §4.2.1).
Associated enhanced codes
The enhanced codes that usually come with this code, per the registry and the providers:

4.2.44.3.14.5.04.2.24.5.3
Source
RFC 5321

How 452 appears at providers

The exact text from the provider's documentation, as you see it in the bounce, and what it means.

452 4.2.2The recipient's inbox is out of storage space.

The recipient's mailbox is out of storage. Only the recipient can make room; the sending server retries for a while.
452 4.5.3Domain policy size per transaction exceeded, please try this recipient in a separate transaction.

The recipient domain's policy limits recipients per transaction; this recipient must go in a separate transaction.
452 4.5.3Your message has too many recipients.

The message has too many recipients for Gmail's limits; split the sending.

Sources: RFC 5321 · RFC 3463 · RFC 3464 · IANA · Gmail · Microsoft 365 · read on 26 September 2026