There can be several reasons why your email may not be getting delivered. One possible explanation is that the recipient’s registry settings or spam filter have been set incorrectly, blocking your emails. Another reason could be that something in the message has made it unsafe to receive. If you are using a bulk mailing service, it can be challenging to avoid sending emails to bulk recipients who no longer want emails from you. In either case, you’ll need to take steps to fix any issues with your email delivery.