Ted Lemon wrote in <CAPt1N1kDJ2qY_13zOv5jcsxYZcOK6Kxn4S3Cb-Zwd-bANCZ2sA@xxxxxxxxxxxxxx>: |That's fair, but it seems like then it might be good to actually say that |in the document. As an implementor I would be inclined to treat a CNAME |here as invalid and ignore it based on the text as written. Indeed i spoke nonsense and missed that this is about domain names that come from exactly MX records. I thought CNAME in general and thought above 5321 2.3.5, which says For example, a domain may refer to an alias (label of a CNAME RR) or the label of Mail eXchanger records to be used to deliver mail instead of representing a host name. See RFC 1035 [2] and Section 5 of this specification. ... Only resolvable, fully-qualified domain names (FQDNs) are permitted when domain names are used in SMTP. In other words, names that can be resolved to MX RRs or address (i.e., A or AAAA) RRs (as discussed in Section 5) are permitted, as are CNAME RRs whose targets can be resolved, in turn, to MX or address RRs. Local nicknames or unqualified names MUST NOT be used. which is "crystal clear". But then i do not understand why you struggle, since then, if it is exactly a domain name returned via a MX record, 5321 as well as the referenced 2181 are also very clear that in that case "never a CNAME RR" may result from looking it up. So *i* am silent now and take back what i said, since i can understand the reasoning why an explicitly placed MX record shall not go over CNAME (again), .. (on the other hand relaxing this and suggesting "an overall loop limit" i could also understand, given how deeply nested for example SPF records and other such new standards explore the DNS). .. --steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt) -- last-call mailing list -- last-call@xxxxxxxx To unsubscribe send an email to last-call-leave@xxxxxxxx
