This is old but I remember someone showed me years ago and I found it interesting but essentially it’s all about filing emails appropriately (things you can deal with next week, in a month, etc), taking care of any right away that can easily then be deleted (out of sight, out of mind) and then getting your inbox as close to empty as possible by the end of your day. https://www.youtube.com/watch?v=z9UjeTMb3Yk