Internet Service Providers (ISPs) like Comcast and Verizon are understandably eager to protect their users from junk email, also commonly referred to as spam. But, in doing so, they often end up blocking or filtering emails from legitimate senders. In other words, your legitimate, non-spam email might NOT get to who you sent it to for no fault of yours. Yes, even if someone subscribed and asked to get your newsletter, even if they confirmed-opted-in, they might never get it! They best way to address this issue to use email marketing best practices in order to improve and optimize deliverability.