How to remove libraries

I’m migrating a project from the command line to ESP. The app doesn’t use email, so I am trying to remove libemail.a from the build. When I go to the project’s Properties, I can go to the Library tab, highlight libemail and click Remove, and it is removed from the list. I click Apply, then Ok, then rebuild my project, and it is still there. Go back to the project properties, and its back. How do I get rid of it?