Attempts to relay mail by issuing a predefined combination of
SMTP commands. The goal of this script is to tell if a SMTP
server is vulnerable to mail relaying. An SMTP server that works
as an open relay, is a email server that does not verify if the
user is authorised to send email from the specified email
address. Therefore, users would be able to send email
originating from any third-party email address that they want.
The checks are done based in combinations of MAIL FROM and RCPT
TO commands. The list is hardcoded in the source file. The
script will output all the working combinations that the server
allows if nmap is in verbose mode otherwise the script will
print the number of successful tests. The script will not output
if the server requires authentication. If debug is enabled and
an error occurrs while testing the target host, the error will
be printed with the list of any combinations that were found
prior to the error. Use this to change the IP address to be used
(default is the target IP address)