exploit05: exploit using smtp service.

command: msfconsole

msf6> search smtp
msf6> use auxiliary/scanner/smtp/smtp_version
msf6 auxiliary(scanner/smtp/smtp_version)> set Rhosts [host]
msf6 auxiliary(scanner/smtp/smtp_version)> run
 #now smtp service is running on metasploitable system.so exit and do nc.
msf6 auxiliary(scanner/smtp/smtp_version)> exit

command: nc [host] port // port -> port on which smtp is running
 # now when u enter (vrfy user), it shows u as one of the user. 
 #using this we can change privilege escalation, i.e, we can chnge this normalshell to rootshell