EC
452
SMTPWARNNotableTemporary Resource ErrorHIGH confidence

Requested action not taken: insufficient system storage

What this means

The 452 code means the server has run out of a required resource, typically disk space, to accept the message. This is a temporary condition, and the client should try sending the message again later.

Why it happens
  1. 1The server's mail queue disk partition is full.
  2. 2The server has hit a memory limit for processing messages.
  3. 3The number of messages in the queue has exceeded a configured limit.
How to reproduce

A client attempts to send a large attachment to a server with a full mail spool.

trigger — this will error
trigger — this will error
DATA
354 Go ahead
[...large email data...]
.
452 4.3.1 Insufficient system storage

expected output

452 Insufficient system storage

Fix

Retry delivery

WHEN When you control the sending MTA

Retry delivery
// Queue for a later attempt, as the storage issue may be resolved
if (smtpCode === 452) scheduleRetry(message);

Why this works

This allows the receiving server's administrator time to free up storage space.

What not to do

✕ Immediately treat as a hard bounce

Insufficient storage is usually a temporary problem that can be fixed. Retrying is the correct protocol.

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