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CNAMES in MX records

Created by dave. Last edited by dave, 12 years and 169 days ago. Viewed 1,681 times. #1
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A Comment About MX Records Pointing To CNAMEs

RFC 1912                   Common DNS Errors               February 1996

Don't use CNAMEs in combination with RRs which point to other names like MX, CNAME, PTR and NS. (PTR is an exception if you want to implement classless in-addr delegation.) For example, this is strongly discouraged:

podunk.xx. IN MX mailhost mailhost IN CNAME mary mary IN A 1.2.3.4

[RFC 1034] in section 3.6.2 says this should not be done, and [RFC 974] explicitly states that MX records shall not point to an alias defined by a CNAME. This results in unnecessary indirection in accessing the data, and DNS resolvers and servers need to work more to get the answer. If you really want to do this, you can accomplish the same thing by using a preprocessor such as m4 on your host files.

Source: >>http://www.ornl.gov/lists/mailing-lists/qmail/1997/09/msg00945.html

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