Tool 189: SMTP server
  
  Description:
   
  This tool is a SMTP server. It only stores commands and messages
  in a local directory. It does not try to forward messages.
  
  Parameter --allowed-clients lists the IP addresses or hosts allowed
  to connect.
  Parameter --src-port defines the local port number to listen on.
  Optional parameter --src-ip defines the local IP address to use.
  Optional parameter --iptype defines which kind of IP address to use
  when --src-ip is unset (accepted values: ip4 and ip6).
  Optional parameter --ip4opts permits to add IP4 options encoded as
  mixed.
  Optional parameter --ip6exts permits to add IP6 options encoded as
  mixed (first byte is the next header number).
  Optional parameters --device and --src-eth are not yet implemented.
  
  This tool may need to be run with admin privilege in order to listen
  on a small port number (port<1024).
   
  Synonyms:
    sendmail, qmail, postfix
  Usage:
    netwox 189 -m dir [-d device] [-E eth] [-I ip] [-P port] [-o ip4opts] [-O ip6exts] [-t iptype] [-T uint32] [-c ips]
  Parameters:
 
  | parameter | description | example | 
 | -m|--maildir dir | mail directory | /tmp | 
| -d|--device device | device name | Eth0 | 
| -E|--src-eth eth | source ethernet address | 0:2:3:4:5:6 | 
| -I|--src-ip ip | source IP address | 192.168.100.200 | 
| -P|--src-port port | source port number | 25 | 
| -o|--ip4opts ip4opts | IPv4 options |  | 
| -O|--ip6exts ip6exts | IPv6 extensions |  | 
| -t|--iptype iptype | type to use when src-ip is unset | ip4 | 
| -T|--timeout uint32 | timeout in ms | 180000 | 
| -c|--allowed-clients ips | clients allowed to connect | all | 
  Examples:
    netwox 189 -m "/tmp"
    netwox 189 --maildir "/tmp"