I like that it's very simple to use, you can set up rules for your customers easily in this software! It also has a great customer support team who is always willing to help you out with any questions or issues you may have - they are knowledgeable professionals at what they do! The only thing I dislike about netbox was their price point compared to other similar softwares available online such as Zoho mail etc., but everything else works well so i'm not sure if there really IS anything wrong here.
We've been using this email service provider since we started our business (about 4 years ago) now and haven't had an issue yet.