Resetting the (non-gmail) email application I am using the non-gmail email application to connect to get email from my university, but the app seems to have a bug and sometimes (probably when there are connection issues) doesn't properly delete emails. These would be deleted from the server, but get stuck in the app. Every time after a refresh operation they reappear even if I delete them over and over again. They reappear even if their date is older than the defined relevant window (e.g. last month). How can I refresh the app to get rid of these zombie emails?
If you don't mind having to completely re-configure it, and start as if you'd just installed that app:


Go to Settings → Apps
Scroll to the app in question, tap it
Select to "Delete Cache" and "Delete Data"


Now you've completely "refreshed" it. With some luck, the app somehow offers to export its configuration; if so, do that first, and re-import the settings after above described "reset" to save you from manually reconfiguring it.