452: insufficient system storage
The receiving server is short of storage or has hit a limit, such as the number of recipients in one message, and asks the sender to try again later.
- Standard
- Provider
- Temporary (4xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 452
- Provider
- Standard SMTP codes
- Temporary or permanent
- TemporaryThe sending server keeps the message and tries again later.
- Who has to act
- Either side, depending on the cause. Start with the checks below that are yours.
- What the server says
452 Requested action not taken: insufficient system storage
What it means
RFC 5321 defines 452 for insufficient system storage, and also names it as the correct reply when a server has reached its limit on recipients in one transaction (the older RFC 821 had listed 552 for that). In the recipient case the sending server is expected to send the remaining recipients in a new transaction, so they still get the message. Servers also send 452 with 4.2.2 for a mailbox over quota. In every case the reply is temporary: the message stays queued and is tried again.
Common causes
- Too many recipients in one message, often shown as 452 4.5.3.
- The receiving server's storage is full, often shown as 452 4.3.1.
- The recipient's mailbox is over its quota, shown as 452 4.2.2.
How to fix it
- 01Let the sending server retry; it should send the remaining recipients separately.
- 02Send bulk mail as one message per recipient.
- 03Read the enhanced code: 4.5.3, 4.3.1 and 4.2.2 point to different causes.
- 04If a mailbox stays full, tell the recipient by another channel.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
- RFC 5321, section 4.2.3: Reply Codes in Numeric Orderrfc-editor.org
- RFC 5321, section 4.5.3.1.10: Too Many Recipients Coderfc-editor.org
Related codes
- 4.5.3Too many recipients.The message lists more recipients than the server accepts in one transaction; the remaining recipients have to be sent in a separate transaction.
- 4.3.1Receiving system out of storage.The receiving mail server has run out of storage space, so it cannot accept messages for now; the sending server keeps the message and retries later.
- 5.2.2Mailbox full.The recipient's mailbox has reached its storage quota, so the server will not take more mail until the owner deletes messages or gets more space.
- 552Storage allocation exceeded.The receiving server aborted the message because it exceeded a storage limit, usually a full mailbox or a message larger than allowed.
452 at other providers
- 452Too many emails in one session.Your server sent more messages in one SMTP session than Xfinity accepts. Xfinity allows 1,000 emails per session, so the rest have to go in a new session.
- 452Too many recipients in one message.The message listed more recipients than Xfinity accepts at once. Xfinity allows 100 recipients per message, so a larger list has to be split.
- 452Too many recipients in one message.Your server named more recipients in one transaction than GMX accepts, currently 20 per message, so the rest were deferred. Split the recipients into several transactions.
- 452More than 100 recipients in one message.Mimecast accepts at most 100 recipients per message transaction and asks your server to send the rest in another batch. Most mail servers do this automatically.
- 452Hourly recipient limit reached.Your server sent more recipients to the company’s Cisco gateway this hour than its rate limit allows. The rest are deferred until the limit resets.
Further reading
All 105 standard codesEvery code in the wikiPaste your own bounce