Chapter 23 WAN Optimization, Web Cache, Explicit Proxy, and WCCP : The FortiGate explicit FTP proxy : Security profiles, threat weight, device identification, and the explicit FTP proxy : Explicit FTP proxy options and SSL/SSH inspection
  
Explicit FTP proxy options and SSL/SSH inspection
Since the traffic accepted by the explicit FTP proxy is known to be FTP and since the ports are already known by the proxy, the explicit FTP proxy does not use the FTP port proxy options settings.
When adding UTM features to an FTP proxy security policy, you must select a proxy options profile. In most cases you can select the default proxy options profile. You could also create a custom proxy options profile.
The explicit FTP proxy supports the following proxy options:
Block Oversized File and oversized file limit
The explicit FTP proxy does not support the following protocol options:
Client comforting