The Messaging Gateway Control Center allows for the selection of FTP as the download protocol for the local LAN host configuration in Malware > Email Scan Settings > Liveupdate. The Liveupdate client, however, will only attempt to download definitions via HTTP and so selecting FTP as the protocol in the LUA server URL will cause malware definition updates to fail.
The option to use an FTP url to connect to LUA has been removed in SMG 10.7.4. The Control Center will now return an error message when attempting to configure Liveupdate to use FTP rather than HTTP.