Thank you.
You can set up sent folder sync in each account's settings.
- Long press the account in the main window (account list)
- Choose Options and Folders
- Scroll down to see the server's folder list (let it refresh the first time, I guess)
- Tap the server's sent folder, choose "Sync with [ Sent ]"
And just in case:
If you don't see "Sync with [ Sent ]" in the popup, just "Incoming" and "Spam", it means the app is not compatible with this server (or, to be more precise - the server does not support the UIDPLUS extension which my app uses to upload and move messages).
I'm working on removing this dependency, making the app compatible with all IMAP servers, this should be done soon-ish.