🚀 go-pugleaf

In article <1992Apr8.164249.10851@husc3.harvard.edu> utterbac@husc10.harvard.edu (Margot Utterback) writes:
>Recently, I contacted a workstation vendor about the mail system
>that comes with the workstation.  The operating system is based
>on System V release 4.  The mail system failed when the host portion
>of an address was an alias or nickname.  The response was that 
>RFC821 and RFC822 specify that the address must be the official
>domain name and that the entries in the host file and any 
>cname records in the DNS are irrelevent.
>
>This seems a little farfetched to me.  First, the rfcs in theis
>case seem to be irrelevent.  Don't they only specify what would
>be in the headers, not the address given to the mailer?  

I find no references to CNAMEs in RFC 821 or RFC 822, so perhaps your vendor
was shooting from the hip. However, assuming you're using SMTP to send the 
mail from one host to another AND assuming that you wish your sending host to 
meet the Internet Host Requirements, then I believe the following section 
from RFC 1123 (Requirements for Internet Hosts -- Application and Support) 
governs:

---

5.2.2  Canonicalization: RFC-821 Section 3.1

         The domain names that a Sender-SMTP sends in MAIL and RCPT
         commands MUST have been  "canonicalized," i.e., they must be
         fully-qualified principal names or domain literals, not
         nicknames or domain abbreviations.  A canonicalized name either
         identifies a host directly or is an MX name; it cannot be a
         CNAME.

---

Under SMTP (as opposed to UUCP or whatever), the RCPT command corresponds to 
"what is given to the mailer", so, yes, you MUST use a canonicalized name if 
you want to pass muster under the Internet Host Requirements.

>Second,
>why limit the address even in the header? You get the host portion,
>ask the DNS what the MX record is.  It will respond with the
>IP address and the canonical name.  Bingo, you have the official
>name, just use that in the rest of the processing.  

I'm not sure whether CNAMEs *ARE* prohibited in the header, given the absence
of mention in RFC 821 & RFC 822. Perhaps someone can clarify?

Even if they are prohibited, perhaps the rationale is that canonicalization
is better done in the MUA rather than the MTA (??)

------------------------------------------------------------------------------
kevin@cfctech.cfc.com 		  | Kevin Darcy, Unix Systems Administrator
...sharkey!cfctech!kevin 	  | Technical Services (CFC)
Voice: (313) 759-7140 		  | Chrysler Corporation
Fax:   (313) 758-8173 		  | 25999 Lawrence Ave, Center Line, MI 48015
------------------------------------------------------------------------------