A webhook is a message HawkOpen sends to a web address you choose whenever something happens. Each message is signed with a secret that only you and HawkOpen know, so the receiving tool can check it really came from HawkOpen. Failed deliveries are retried a few times.
If you do not use a CRM yet, the Pro and Business plans include HawkOpen’s own simple CRM; on Free it is a paid add-on with a 21-day trial. Many CRMs also offer their own email tracking; if you track in two tools at once, the same email gets two sets of tracking elements.