This article explains the configuration of Acronis Files Connect (formerly ExtremeZ-IP) to support guest access.
In Windows, the Anonymous Logon group is not a member of the Everyone group by default.
In order to enable guest access, Acronis Files Connect requires that the Anonymous Logon group be a member of the Everyone group.
To change this setting, launch the Local Security Settings (sometimes called Local Security Policies) administrative tool. Navigate to Local Policies -> Security Options and set the "Network access: Let Everyone permissions apply to anonymous users" setting to "Enabled".
In the file system, the Everyone group will need to be granted rights to any data guest users are expected to work with.
Note: You must restart the Acronis Files Connect service to have this change take effect.