How do I setup DNS to reduce my outbound mail being tagged as spam

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Joel Stidley Posted: 09-05-2006 11:05 AM

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Many companies employ simple measures to reduce inbound spam by checking to make sure the server sending them email is properly configured in DNS.  If you do not have this configured properly you might have problems when sending outbound email. 

The list below is a simple walk through of properly configuring a single exchange server.

1.  The Exchange server should have its own SNAT setup.  If are using a lower end firewall you may have to use the default external NAT address of your firewall.  This is not ideal but it will work.  It is assumed that you already have 25/tcp open in and outbound for this address.

2.  Determine the name the server will have.  If it is a mail server for your company with an email domain of notaspammer.org you might want to call it mail.notaspammer.org.  You could also just choose a name using the current
machine name like exchange01.notaspammer.org.  You will want to choose a
name that does not conflict with any of their other host names and must be
valid for the internet.

3.  Modify the server to report that name. 
          Open Exchange System Manager
          Navigate to the SMTP Virtual Server
          Choose "Properties" on the SMTP Virtual Server
          Click on the "Delivery" tab
          Click on the "Advanced" button
          In the fully qualified domain name box type the hostname that you chose.
          Click OK
          Click OK
          Restart the SMTP Service

4.  Configuring DNS

• Add a PTR (reverse) record for the server hostname for the SNAT address.  Since your ISP most like controls the reverse DNS you will    probably need to contact your ISP to make this change
• If not already done add an A record for the server hostname for the SNAT address