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Hi there,

I am specifically wondering how Customer.io handles delivery. Is there a threshold of a certain amount of messages per hour or second? What is the maximum send rate?

Hi Jeff! 👋

Customer.io can send about 1 million emails per hour/16k per minute. There are other things to consider such as inbound thresholds per-provider that our email provider, Mailgun, takes into account.

Newsletters by default can send with the maximum sending rate however, we do have the ability to set your own send rates. When send rate is limited, messages will be queued for delivery in batch sizes of the number you specify. Every day/minute/hour after the newsletter is scheduled to be delivered, one of those batches will be sent, until all sending is complete.

I hope this helps! 


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