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How can I ensure my Email Security Gateway is compliant with the new rDNS, Banner and MX verification processes for outbound mail?

  • Type: Knowledgebase
  • Date changed: 7 months ago
Solution #00005902

This solution applies to the Email Security Gateway, all firmware versions.

The following documents how to ensure compliance with the new rDNS, Banner, MX verification process for outbound mail:

Many companies are now starting to check the domain name that the sending IP address lists against all of the available sources associated with that particular domain. If it does not match, the server is rejecting the connection.

This does not follow any RFC documentation, and is something new that some individual domains/mail servers are doing. Domains/Mail Servers are not required to accept mail from a sender, and can create any rules or requirement that they like to prevent mail. This is a method some are using to try and prevent spammers. As with the PTR record, it is something that everyone will have to do to ensure that their mail is delivered correctly.

To make sure that all of your settings are compliant you should configure the following: 
  1. The A record for your Barracuda needs to end in <your_domain_name>.
  2. The PTR record for your Barracuda IP address needs to end in <your_domain_name>.
  3. The MX record for your Domain needs to end in <your_domain_name>.
  4. The Default domain on your Barracuda needs to be <your_domain_name>.
  5. The SMTP Banner of your Barracuda needs to be <your_domain_name>. If you are using a custom SMTP Banner we recommend using this:
    • <your_domain_name> ESMTP (<server_id>)
    • Where the <server_id> is the identifier for your server. 
    • If you leave out the Banner the Barracuda will use its hostname which will end with the set default domain.
The above changes will ensure that you are compliant with all current anti-spam functions that people are developing around domain name verification.

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