Hi, We have been receiving a number of bounce back's from mail servers performing a reverse lookup of our address and failing. Currently we have an A record that points to mail.ourcompany.com, this ties back to an external IP address for our exchange server 192.192.192.3 so that our Outlook web access users can use a HTTPS connection in a web browser to get into their mail remotely. We also have an MX record that points to mail.ourcompany.com. Exchange is setup to use mail.ourcompany.com as its external FQDN under Protocol/SMTP/delivery/advanced settings and a masquerade of ourcompany.com. The problem is when we read the headers of an email sent to a test POP3 account we are getting the external IP address of our firewall 192.192.192.2, this is the reason we are getting bouncebacks from clients who are obviously performing a reverse lookup and failing. I can't change the A record to point to 192.192.192.2 because this will firstly expose the firewall login page (not good!) and secondly OWA will stop working. So how can I resolve this issue?Thanks, Cep

Hi, Firstly, please let me know whether I understand your problem correctly: 1. At external DNS server, an A record exists point mail.ourcompany.com FQDN to 192.192.192.3 2. Nevertheless, when you send email to external recipient, the source IP Address is 192.192.192.2 and the FQDN configured on the SMTP Server is mail.ourcompany.com. 3. When you send message to external recipient, the messages are bounced back due to Reverse Lookup failed. If I am off base, please let me know. At this time, I suggest you modify the FQDN of the SMTP Virtual Server to mail1.ourcompany.com. Then, please create an A record for mail1.ourcompany.com point to 192.192.192.2. Please also create a PTR record for 192.192.192.2 which point to mail1.ourcompany.com on external DNS server. For your reference: http://support.microsoft.com/kb/300171/en-us Mike

Hi, Any further question regarding the issue?Mike

Hi Mike, Sorry for the late reply I have actually been away on holiday! First day back so, back to business, yes you have the general jist of the issue except that the external DNS is outside our control. We have a domain name hosted with an external company, we are able to create A, NS, MX and CNAME records via their control panel and once these changes are made I believe their DNS records will update over a few hours. If I modify the FQDN as you suggest of the SMTP virtual server does this then mean that people will no longer be able to access OWA via mail.ourcompany.com as to be honest this is where the main sticking point is. Cheers DavidThanks, Cep

Hi David, I would like to explain that after changing the SMTP Virtual Server FQDN, we should have two DNS A records: mail.ourcompany.com 192.192.192.3 mail1.ourcompany.com 192.192.192.2 The users should still be able to access their OWA by using mail.ourcompany.com FQDN Note: The users access OWA though IIS web service and I think that it does not relate to which SMTP Virtual Server FQDN is. When send email to external recipients, the FQDN mail1.ourcompany.com is provided to remote mail server and associated with IP Address 192.192.192.2. Mike

Thanks Mike! That appears to have worked nicely :)Thanks, Cep