Outgoing mail refused after a threshold.
WHAT IT MEANS
Shared hosting enforces an hourly sending limit. Once reached, further messages are refused until the hour passes.
WHY THE LIMIT EXISTS
One account sending in volume affects the sending reputation of every account on the server.
WHAT USUALLY CAUSES IT
A newsletter sent through hosting mail rather than a proper service An application sending in bulk A compromised account sending spam A mail loop between forwarders
CHECK WHETHER IT IS YOU
cPanel > Track Delivery. Look at what was sent and to whom.
Volume you do not recognise means the account is compromised. Change every password and open a ticket immediately.
FOR LEGITIMATE BULK SENDING
Use a dedicated sending service: SendGrid, Brevo, Mailgun or similar.
They handle bounces, unsubscribes and deliverability, and they are not subject to hosting limits.
Add their SPF and DKIM records so your mail authenticates.
MAIL LOOPS
Two forwarders pointing at each other generate enormous volume quickly. Check your forwarders.
