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.
I had exactly the same problem myself. The default android app for email took up a lot of storage space. When I tried to clear the Data from the app menu (Settings->Apps->Email) the "Clear Data" button was greyed out.
The process below will reset you connection to you email account, so make sure you know your password and settings so you can reconnect at the end.
I found that the Exchange Email server acquires some security settings, and this leads to the greyed-out option. What you need to override these settings is to go to Settings->Security, scroll to down and click on "Device administrators". You will find a list of programs with special security options, and one of them will be "Email". Uncheck the "Email" program. Once you do this your e-mail account will be reset and deleted and the space that the app takes will be cleared.