The PrivacyOptions option allows you to set certain privacy flags. Actually, many of them don't give you any extra privacy, rather just insisting that client SMTP servers use the HELO command before using certain commands or adding extra headers to indicate possible spoof attempts.
The option takes a series of flag names; the final privacy is the inclusive or of those flags. For example:
O PrivacyOptions=needmailhelo, noexpnThis insists that the HELO or EHLO command be used before a MAIL command is accepted and disables the EXPN command.