Mail not in sync (webmail vs iOS ActiveSync vs macOS IMAP vs Android ActiveSync)

Mail not in sync (webmail vs iOS ActiveSync vs macOS IMAP vs Android ActiveSync)

I read my mail on 4 places:

- webmail
- iPad ActiveSync
- Android ActiveSync
- Mac Mini IMAP

Not all 4 places are in sync. For instance my inbox on Android is empty, but there is stille one mail on the other 3 places. Other example: Trash on my iPad has 10 messages on the other 3 places 8 messages. 

Waiting overnight does not resolve the issue, the before mentioned examples remain the same.

Any solutions?