Netcore maintains a list of phishy domains based on the spam complaints history and blocks emails sent to these domains in order to safeguard your emails and your domain reputation. This helps in boosting your domain reputation over the internet by not sending emails to any email ids of these domains.
In case you find any valid domain is part of the same list due to which you are facing problems with the delivery of your emails please let us know on 24X& chat support or drop us an email to support@pepipost.com along with the details so that we can get it fixed for you.