At 9:27 PM -0500 4/10/07, Brad Knowles wrote: > The important sentence here is: > > | In the dot-atom form, this is interpreted as an Internet > | domain name (either a host name or a mail exchanger name) as > | described in [STD3, STD13, STD14]. > > In particular, note that it says "host name" or "mail exchanger name", > and specifically omits "CNAME alias", and refers you to STD3 (RFCs 1122 > and 1123) and STD13 (RFC 1034) for definitions of these terms.
In contrast, here's a quote from the cf/README file for sendmail 8.13.8: | confDONT_EXPAND_CNAMES DontExpandCnames | [False] If set, $[ ... $] lookups that | do DNS based lookups do not expand | CNAME records. This currently violates | the published standards, but the IETF | seems to be moving toward legalizing | this. For example, if "FTP.Foo.ORG" | is a CNAME for "Cruft.Foo.ORG", then | with this option set a lookup of | "FTP" will return "FTP.Foo.ORG"; if | clear it returns "Cruft.FOO.ORG". N.B. | you may not see any effect until your | downstream neighbors stop doing CNAME | lookups as well. And the HISTORY file for postfix-2.4.1-RC1: | 20021207 | | Performance: RFC 2821 blesses the use of CNAME domain names | in MAIL FROM and RCPT TO. Not having to expand CNAME domain | names speeds things up a bit. File: smtp/smtp_proto.c. Now, I'm still not seeing the part that Wietse is referring to. I'm still checking the document. However, Eric's comment in the sendmail cf/README file makes it plain that this is a common behaviour that has been done for as long as Internet e-mail has existed, and therefore it's going to be a very, very long time before we can assume that most sites won't do this kind of thing -- even if the IETF does finally codify the practice. So, we're still going to need a FAQ on this subject, regardless of whether the then-current RFCs require that CNAME aliases be resolved to their actual canonical names or not. -- Brad Knowles <[EMAIL PROTECTED]>, Consultant & Author LinkedIn Profile: <http://tinyurl.com/y8kpxu> Slides from Invited Talks: <http://tinyurl.com/tj6q4> ------------------------------------------------------ Mailman-Users mailing list [email protected] http://mail.python.org/mailman/listinfo/mailman-users Mailman FAQ: http://www.python.org/cgi-bin/faqw-mm.py Searchable Archives: http://www.mail-archive.com/mailman-users%40python.org/ Unsubscribe: http://mail.python.org/mailman/options/mailman-users/archive%40jab.org Security Policy: http://www.python.org/cgi-bin/faqw-mm.py?req=show&file=faq01.027.htp
