452: hourly 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.
- Cisco Secure Email
- Provider
- Temporary (4xx)
- Class
- Sources checked
- Author
At a glance
- Code
- 452
- Temporary or permanent
- TemporaryThe sending server keeps the message and tries again later.
- Who has to act
- The sender. The fix is on the sending side: your domain, your server or your list.
- What the server says
452 Too many recipients received this hour
What it means
Cisco Secure Email Gateway can cap how many recipients per hour it accepts from one remote host, and this is its default reply when a host goes over. The limit is set by the receiving company to suit its size, and Cisco notes that when one host in a /24 network goes over, the gateway can block the others in that range as well. The reply is temporary: your server holds the extra messages and retries, and they are accepted once the hourly count allows. Sending harder only prolongs it.
Common causes
- A large send to many people at one company within an hour.
- Another server in the same /24 network went over the limit, which can block yours too.
- A low hourly limit configured by the recipient company.
How to fix it
- 01Let your queue retry; deferred recipients are accepted as the hourly window allows.
- 02Spread sends to that company over several hours.
- 03If you are a known partner with regular volume, ask the recipient’s IT team for a higher limit for your servers.
Sources
What this page rests on, checked on 20 Oct 2026. The explanation is ours; the reply text is the server's.
Related codes
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.
Further reading
All 7 Cisco Secure Email codesEvery code in the wikiPaste your own bounce