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obonaventure / cnp3

Computer Networking : Principles, Protocols and Practice (first and second edition, third edition is being written on https://github.com/cnp3/ebook)
https://www.computer-networking.info
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Electronic mail - Server preference #144

Closed fthuin closed 9 years ago

fthuin commented 9 years ago

In the ebook, electronic mail part, it is said " The DNS can return several MX records for a given domain. In this case, the server with the lowest preference is used first. If this server is not reachable, the second most preferred server is used etc."

Shouldn't it be "the server with the highest preference is used first" ?

obonaventure commented 9 years ago

RFC2821 contains the following in section 5:

Multiple MX records contain a preference indication that MUST be used in sorting (see below). Lower numbers are more preferred than higher ones.