Hi Phil. Am Sonntag, 20. Mai 2007 21:51:04 schrieb Phil Pennock: > On 2007-05-19 at 15:34 +0200, Peter Thomassen wrote: > > $ host -t mx mail.peter-thomassen.de > > mail.peter-thomassen.de MX 10 mail.a4a.de > > mail.peter-thomassen.de MX 20 rescue.a4a.de > > $ host -t mx mail.glv.at > > mail.glv.at CNAME glv.at > > glv.at MX 10 mail.a4a.de > > glv.at MX 20 rescue.a4a.de > > $ > > This, unfortunately, is broken. The hostname provided by MX resolution > is not permitted to be a CNAME record; it may work for some combinations > but other clients won't support it, so you'll not be reachable by some > people (those following the standards carefully). > > Another useful and readable RFC which is relevant here is: > RFC 1912 Common DNS Operational and Configuration Errors > and section 2.4 of that covers CNAME usage, including covering the issue > with MX records, providing pointers to the relevant standards-track RFC > comments on the issue.
In RFC 1912, I can only find that MX records themselves shall not point to CNAME type hostnames. However, I cannot find that the host whose MX server we are looking for may not be a CNAME alias. The hostname provided by MX resolution is mail.a4a.de (rescue.a4a.de) which is not of type CNAME. I have read section 2.4 several times now. If I got it wrong nonetheless, please give me a quote :-) Maybe, mail.glv.at was a bad example, and we should rather investigate sub.glv.at: $ hostx -t mx sub.glv.at sub.glv.at CNAME glv.at glv.at MX 20 rescue.a4a.de glv.at MX 10 mail.a4a.de $ Have a nice day. -- Peter Thomassen • Steigerwaldstr. 4 • 97076 Würzburg • Germany http://www.peter-thomassen.de/ • [EMAIL PROTECTED] fon +49-931-2705351 • mobil +49-176-63159879
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