I have a dockerized mailcow server for over a year, never solved the client sync problem. Using windows mail on windows or gmail app on android, only the last 30 days of messages are synchronized.
Trying to use Thunderbird on windows all emails are synchronized.
Is it a problem with the server or with the clients?
How can I fix this?
Have a look at the configurations on Android and possibly also on Windows Mail.
If you go via ActiveSync, the time can be set.
I, for example, never synchronise more than one month to my smartphone.
I hope I have been able to help you a little.