# Need to rebuild app after changing app.yml? **URL:** \ **Category:** Self-hosting\ **Created:** [21. März 2016 um 15:10 UTC](https://meta.discourse.org/t/need-to-rebuild-app-after-changing-app-yml/41370 "2016-03-21T15:10:59Z")\ **Posts on this page:** 1\ **Showing post:** 3
**Author:** ![JimmyX](https://sea3.discourse-cdn.com/meta/user_avatar/meta.discourse.org/jimmyx/32/52302_2.png) [@JimmyX](https://meta.discourse.org/u/JimmyX)\ **Post date:** [22. März 2016 um 07:42 UTC](https://meta.discourse.org/t/need-to-rebuild-app-after-changing-app-yml/41370/3 "2016-03-22T07:42:51Z")
I want to develop. I was confused trying to set up SMTP so I could create (and then email confirm) a new user. The docs talk about app.yml which comes from standalone.yml. These files are not in the developer install. So I grabbed them from the docker install and things went downhill from there. What I needed instead was to run bundle exec sidekiq \>& /dev/null & mailcatcher --http-ip=0.0.0.0 Then in a browser, go to [http://localhost:4080](http://localhost:4080). Sent emails will be received by mailcatcher and shown in its web ui. When you catch the email with confirmation link change localhost:3000 … to localhost:4000 … and paste that into the browser. It was as simple and intuitive as that 😉 --- _[View the full topic](https://meta.discourse.org/t/need-to-rebuild-app-after-changing-app-yml/41370)._