If you are sure that your *device's* time zone settings are correct --
-- let's check what's reported by the server.
Please long press the account -> Diag: message dates -> select the Inbox (I suppose) and run this to completion.
The app will prompt to email me a log file, do that.
Please include information on a few specific messages, their time values as seen in the app, what you expect them to be instead, and also on your phone's actual time zone value (GMT +/- how much).