I received an email saying Webhook was dropped. Why was it dropped?

Acme allows you to set up as many webhooks for event triggers as you want, but will execute only 1000 webhook requests in one hour. So if you schedule more than 1000 in one hour, you will hit your rate limits, and any webhook calls beyond your rate limit will be postponed to the next hour. 

If more webhooks are triggered within the hour, then depending on the timing, the excess webhooks from the previous hour may be postponed or executed. If a webhook is postponed from execution for more than 24 hours, then it will be dropped.