Why not all emails are delivered?
Our system will automatically suppress sending emails to unengaged contacts in order to protect the sender's IP reputation. There is a way to lift suppression from unengaged contacts. If you want suppression to be lifted on your account, please contact support or your project manager
Please note that email suppression is set to protect the sender's IP
reputation and deliverability rate. When contacts receive emails that they
do not open it for a prolonged period of time it will damage your IP
reputation and email providers will start placing emails send from your IP
address in a recipient's spam box.
How to send emails to unengaged clients when suppression is lifted: