If you are using Mac 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 the System Settings:
Open the Apple ID section:
Click on the iCloud on the right hand menu:
Find Mail app in the list of apps, which are using iCloud:
If the Mail app is disabled/set to OFF in the iCloud section in your System Settings, then it should be disabled under Xink app Preferences too:
If the Mail app is checked/set to ON in the iCloud section in your System Settings, 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.