Trying to whittle down an inbox of 130 to 0 is intimidating. You can knock off 20 and it doesn’t feel like you made any progress. It would be useful if an email app had a “help you to get to inbox zero” mode where it would only show you 20 emails at a time. Once you knocked those out, 20 more fill in. This way you can see the progress you are making on a small scale (from 20 to 18 to 13 to 7 to 0) and stay motivated to keep knocking them out on a large scale.