I'm admin for email list hosted on a mailing service. There seems to be no settings for character encoding there; IIUC, the encoding is set by the sender and the list just flushes it through. There are some users, whose messages are garbled (the language is not English), because their messages are us-ascii encoded rather than utf-8.
At least some senders of those garbled messages use Gmail application on Android. As I don't myself have an Android phone, I don't know where you can set the encoding. Screen shots appreciated.