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How should a customer configure multiple destination servers for a single domain on the Email Security Gateway?

  • Type: Knowledgebase
  • Date changed: 10 months ago
Solution #00003030

All Email Security Gateways, firmware version 3.5.11 and above.

Multiple email servers can be specified for a particular domain for load balancing and a failover email server can be designated for use whenever the destination email server for a domain is unreachable. This can be configured in Basic > IP Configuration for a global setting or in Domains > Edit Domain for a per domain setting. Each entry in a list delimited by commas (",'') or semi-colons (";'') will used in round-robin fashion, with relative weights determined by the number of times a particular entry is listed. A list separated by spaces (" '') will be treated as a failover list, with an entry getting used only if all entries preceding it in the list are unreachable.

For example, to add two failover servers, separate them with spaces like this:

server1 server2 server3

In this example, server2 will be used if server1 is unavailable, and server3 will be used if server1 and server2 are unavailable. The failover should either instant or the time it takes the Barracuda to time out. To load balance destination servers for a single domain, separate them with commas or semicolons like this:


In this second example, mail traffic will be distributed evenly among these three servers. If you wanted 50% to go to server1, 25% to go to server2, and 25% to go to server3, you would enter server1 twice to give it twice as much weight, like this:


or like this:


Weight is assigned irrespective of the order entered.


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