DNS MX Record Priority

benners70
benners70 used Ask the Experts™
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Can someone please clarify how the priority functions in an MX Record. My understand was that if the lowest priority record failed to deliver, the email was then routed to the next highest priority record. I've since been told that actually the email is sent to both records. Which is correct?

The configuration in question is:
smtp.mydomain.com. PRIORITY 5  (IP of my local Exchange Server)
mail.mydomain.com. PRIORITY 15  (IP of WebServer with POP box)

The thinking behind this was if the local exchange was offline then we would get the mail sent to the POP box and would use Exchange to download from the POP on a schedule.

Can someone please clarify?
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Awarded 2009
Top Expert 2010
Commented:
That's correct, if the first record is briefly unavailable or under load then the second record will be used.

The priority system is not reliable on MX records.
Awarded 2009
Top Expert 2010

Commented:
Also see here for a good article from Mestha: http://blog.sembee.co.uk/archive/2007/02/02/38.aspx

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Commented:
Thank you that post was very useful.
Awarded 2009
Top Expert 2010

Commented:
Excellent, let me know if you hve any further questions.

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