If you are using Apple Mail you need to make sure that the iCloud Drive setting is correct.
Under Xink App Preferences there is a setting for iCloud "I'm using iCloud Drive". "I'm using iCloud Drive" should be enabled only if your Mail app is using iCloud.
You can check this in the System Preferences on your MAC:
Go in System Preferences.
Open Apple ID section:
Click on iCloud in the left hand menu:
Find Mail app in the list of apps, which are you using iCloud:
If Mail app is disabled in iCloud section in your System Preferences, then it should be disabled under Xink app Preferences too:
If Mail app is checked in iCloud section in your System Preferences, this means that it is using iCloud and accordingly a setting for iCloud "I'm using iCloud Drive" under Xink app Preferences should be enabled as well.