My exchange server subscribes to the three blacklist providers, and over the weekend we stopped receiving ALL email. In researching this further, I found that removing the DNSRBL blacklist solved the issue.
That said, I was getting email returned sending through hotmail (and gmail for that matter) to our email server showing that an IP address registered to hotmail.com had been blocked. Did anyone else experience this?
Reporting-MTA: dns;bay0-omc2-s5.bay0.hotmail.com
Received-From-MTA: dns;BAY122-W23
Arrival-Date: Mon, 1 Dec 2008 07:43:28 -0800
Final-Recipient: rfc822;josh@*********.com
Action: failed
Status: 5.7.1
Diagnostic-Code: smtp;550 5.7.1 65.54.246.141 has been blocked by DNSRBL