Nosocks, socksuserpassword Channel Options

From MsgServerDocWiki

SOCKS connections (nosocks, socksuserpassword)

SOCKS connections (see RFC 1928 and RFC 1929) can be used to traverse a firewall that would not normally permit outbound SMTP message traffic. If the firewall offers a SOCKS service, then one can connect to the firewall's SOCKS server and authenticate, pass over the remote host name and remote port to which one wishes to make an SMTP connection, and then the SOCKS server on the firewall will make the remote connection and transform the SOCKS connection into the desired SMTP connection. nosocks, the default, specifies that no SOCKS connection will be used.