Backup/eDiscovery not show all accounts

Backup/eDiscovery not show all accounts

Hello,

I tried to find but I didn't get any information about...
In my job we use Zoho mail and we have different sizes of mail boxes, like 10GB, 30GB and some with 50GB.
When I try to configure Backup/eDiscovery function, not show all boxes, but only two with 50GB size.
Now I ask: is there no backup/ediscovery feature for all mail boxes?
Thanks for reply!