Hello Yolanda,
Welcome to the forums, removing an app from your cell phone will not affect your desktop mail, you would remove the app the same as any app on an IOS phone or Android. If you are not able to delete the app like Apple mail which is a built in app then you will only need to sign out of your accounts from the settings>accounts page.
Let me know what kind of device you have and what mail app you are using so I can better assist.