Our email goes through MXLogic for spam filtering and is then forwarded to our Exchange server behind an external Cisco Router - through the Firewall and then internal Cisco Router. We've never had a problem until today. They changed their IP's and required a new set up for DNS MX records. We made the changes but external email no longer comes through. They said there may be a problem with our Pix firewall. Is there a way to tell if it's bouncing the email back? Is there logging I can turn on. I have over 400 users not receiving email - it's critical that I get this working - any suggestions would be appreciated.