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Applies To: Model 500
There is no limit to the amount of MX records available within DNS. It is entirely up to a customer how many systems should receive mail from the Internet and how those mail systems are setup. Using one ePrism will help filter SPAM and malicious content, but is not an ideal solution. E-Mail is a mission critical application that needs to be available 7x24x365. To accomplish this, more then one ePrism unit is required.
What to do:
A minimal redundancy configuration would require a customer to specify two MX records in DNS, each assigned to a separate ePrism. More then one ePrism is required to match this setup. It is highly recommended that all customers start with this setup.
One example of providing a high availability solution to ensure e-mail is always available is to use four MX records. The first two MX records would have equal preference values, allowing mail to be delivered in a round robin style across the two machines. The remaining two MX records would be set with a higher preference value in case the first two did not respond. If one of the first two MX records had failed, the unit with the lower preference value would still receive mail, unless it stopped responding, which the MX records with the higher values would begin to respond automatically. Ideally, these MX records would be geographically dispersed to provide robust e-mail architecture for any organization.
There is flexibility, don't have to follow, can modify to own liking.
What not to do:
Specify two or more MX records in DNS, but have them all refer back to the same physical ePrism. In this case, if the one ePrism were to fail, there would be no secondary unit to fall back to, regardless of the additional MX records available. The company would stop receiving e-mail until the one ePrism was brought back up and running.
Have one MX record specified with one ePrism assigned to it. In this case, if the one ePrism were to fail, there would be no secondary unit to fall back to. The company would stop receiving e-mail until the one ePrism was brought back up and running.
