Al:
If you read RFC 2181 section 10.3, RFC 1034 section 3.6, RFC 1912 (page 6), the average person would understand that it's strongly discouraged. Perhaps "illegal" is too strong a word, but the weight of the RFCs and best practices appears to disagree with your assessment that "there is no such standard nor requirement prohibiting the use of CNAME/alias in an MX record.". Frank From: bind-users-boun...@lists.isc.org [mailto:bind-users-boun...@lists.isc.org] On Behalf Of Al Stu Sent: Sunday, January 25, 2009 12:11 AM To: bind-users@lists.isc.org Subject: BIND 9.6 Flaw - CNAME vs. A Record in MX Records are NOT "Illegal" BIND 9.6 'named' throws the following message during startup claiming that it is illegal to use a CNAME/alias in the MX record. I beg to differ. There is no such standard nor requirement prohibiting the use of CNAME/alias in an MX record. Message thrown at startup: "named[3307]: zone MyDomain.com/IN: MyDomain.com/MX 'MX1.MyDomain.com' is a CNAME (illegal)" Additionally in Chapter 6 - BIND Configuration Reference, Zone File, Discussion of MX Records states the MX records "must have an associated address record (A or AAAA) - CNAME is not sufficient." Some people seem to think RFC 974 creates a standard which prohibits the use of CNAME/alias in MX records. But very much to the contrary RFC 974 demonstrates that CNAME/alias is permitted in MX records. ISC's message that a CNAME/alias in an MX record is illegal is incorrect and just an attempt by ISC to get people to go along with what is only a perceived rather than actual standard/requirement, and should be removed so as not to further the fallacy of this perceived perception of a standard/requirement, as it is neither a standard nor a requirement, and certainly not illegal. Al Stu
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