I use the desktop app without any problems but the Android ZOHO mobile app could use some fine tuning or I am missing some functionality. 

1. The app doesn't fetch mail unless you open it which means no message on the icon like the desktop app..  I use a Samsung Galaxy S9+.  Before switching to the ZOHO app, I used the Samsung mail app. It could be set to fetch mail at different settings and new mail would register on the icon.

2. I have Categories (Distribution Lists) setup.  However, the ZOHO mobile app does not appear to be able to access them which means I can't send mail using a distribution list.