Inbound rate limiting at the SMTP listener

You can choose to enable your own rate limits at the inbound SMTP listener to no more than n messages an hour. This ensures that if one of your systems is hijacked by an attacker, the number of messages they are able to send is limited. You can then react before any damage is too widespread.

By default, we apply an inbound rate limit of approximately one message each second, around 100,000 messages each day. If you have not agreed a different configuration with us and you exceed this rate, our inbound SMTP injection point temporarily throttles the message flow from your local SMTP forwarder. Your SMTP forwarder should be able to manage this behavior, however, by queuing and retrying the affected messages later. This is a standard feature of any SMTP forwarder (MTA).

If 100,000 messages each day is not enough for your needs, please get in touch with your usual contact at Contactlab, so we can provide adequate resources and modify your SmartRelay configuration to better suit your needs.

See SmartRelay overview for more about the SMTP listener, the SMTP injection point and the local SMTP forwarder.

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