FTGate implements strong anti-spoofing features. This means that it will not accept mail from any address that it hosts unless the connection is authenticated by SMTP or the Security Policy AA flag.
450 4.7.1 Please authenticate and try again (#3.21)
If a user gets this error then they must enable SMTP authentication in their mail client.
If an automated machine causes this error then add the address of the sending machine to the Global Security Policy with the following options:
Flags: PA and AA
If neither of the above are appropriate then you must enable spoofing in the security policy options.