I am currently administering an Exchange 2003 server for a small company running on Small Business Server. 2 weeks after starting at this job, the Exchange server was hit with a huge amount of spam email (I now believe the server was left as an open relay, which I have now turned off). The IP address was blacklisted in a couple of places and our rating on IronPort (senderbase) for the IP address was poor, it is now back to good. A residual problem left over after all of this is being unable to send to email addresses that seem to be hosted by google (servers that use mx.google.com) mail servers. When i telnet to these email addresses from the server, mx.google.com is happy with helo/ehlo commands and rcpt commands etc. But when sending from an outlook client, an undeliverable message arrives back within 2 mins.
There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<mail.ourserver.com.au #5.5.0 smtp;550-5.7.1 [18.104.22.168 1] Our system has detected an unusual rate of>
Are we blacklisted by google? What could be stopping the server recieving? Our mx records check out with FQDN and IP address. I have checked all settings in the SMTP area of exchange, wondered if it is DNS??? I am really at the end of my limits. HELP!!!!!!
Any ideas much appreacieated. Thanks for reading.