title: The IP you're using to send mail is not authorized to send email directly to our servers
body: <p>hi i wanted to send mail via smtp protocol to one of my
  gmail's accounts...</p>
  
  <p>i tried but finally it occurred and error :</p>
  
  <pre><code>telnet&gt; open alt4.gmail-smtp-in.l.google.com 25
  Trying 74.125.131.27...
  Connected to alt4.gmail-smtp-in.l.google.com.
  Escape character is '^]'.
  220 mx.google.com ESMTP b4si2095585vdw.57 - gsmtp
  HELO stackoverflow.com
  250 mx.google.com at your service
  MAIL FROM: &lt;test@stackoverflow.com&gt;
  250 2.1.0 OK b4si2095585vdw.57 - gsmtp
  RCPT TO: &lt;■■■■@gmail.com&gt; // filtered ;)
  250 2.1.5 OK b4si2095585vdw.57 - gsmtp
  DATA
  354  Go ahead b4si2095585vdw.57 - gsmtp
  test
  ok
  it done
  .
  550-5.7.1 [5.22.81.102] The IP you're using to send mail is not authorized to
  550-5.7.1 send email directly to our servers. Please use the SMTP relay at your
  550-5.7.1 service provider instead. Learn more at
  550 5.7.1 http://support.google.com/mail/bin/answer.py?answer=10336 b4si2095585vdw.57 - gsmtp
  Connection closed by foreign host.
  </code></pre>
  
  <p>so now how can i send mail without having this problem ?</p>