The reply rate limit is the ceiling to not exceed in order to keep all the benefits of email warm-up.

The average reply rate is between 30% and 45%, this is why it is risky to hit more than that and even more to get a 100% reply rate.

Exceeding this rate would alert email providers that your inbox activity is suspicious and it might hurt your deliverability. In order to avoid such a situation, the reply rate is therefore limited to 45%.