Up-to-date Views For Folders
The counter does refresh for folders, but the folder view doesn't. Currently, you have to select another folder and then come back to it in order to see up-to-date content in the folder. This is a basic functionality that is sorely missed. Preferences/Accounts allows you to set Inbox refresh but not folders refresh time. It appears that it was an option at some point but removed? (see screenshot). I moved from Mac Mail to Airmail due to instability issues, but this is making me want to go back to Mail or find another option altogether.
