Gmail Blacklist or Spam Box?
First, make sure you have a blacklist problem. If Gmail is blacklisting your server’s IP, their servers send one of these bounce messages:
421-4.7.0 unsolicited mail originating from your IP address. To protect ourn421-4.7.0users from spam, mail sent from your IP address has been temporarily 21-4.7.0 rate limited. Please visit
http://www.google.com/mail/help/bulk_mail.n421 4.7.0 html to review our Bulk Email Senders Guidelines. l41si55243084eef.158 - gsmtp
or
Remote host said: 550-5.7.1 Our system has detected an unusual rate of unsolicited mail originating from your IP address. To protect our users from spam, mail sent from your IP address has been blocked. Please visit
http://www.google.com/mail/help/bulk_mail.html to review our Bulk Email Senders Guidelines.</pre
Gmail sends these messages when you are blacklisted; they do not send any notices regarding spam box placement.
