Kaspersky Small Office Security that is installed on a file server is compatible with Kaspersky Security for Microsoft Exchange Servers 9.0 Maintenance Release 5 (including hotfix 1) and Kaspersky Security for Microsoft Exchange Servers 9.0 Maintenance Release 6. For proper operation of Kaspersky Small Office Security File Server together with those applications:
Disable Mail Anti-Virus.
Disable Web Anti-Virus or in the Web Anti-Virus settings add the web addresses of Exchange Web Services to the list of trusted URLs (Web Anti-Virus settings → Advanced Settings → Trusted URLs).