On Fri, Apr 26, 2002 at 04:34:51PM -0400, Ed Abrams wrote: > I have a weird question. Suppose that you have something like this: Client > C, using Email Client E, sending email message M, via his ISP SMTP relay S, > to user at host T. That's all normal. But here is where things get > interesting. > > Suppose that T does not have an MX record, but *does* have a CNAME alias to > a host R. Thus, when S looks up the MX for T, nothing comes back. My > questions: > > 1) does a standard govern what happens?
yes, S should rewrite the recipient's address domain part to what the CNAME pomits to and deliver to the server listed in the MX records for the CNAME target otr its A-record if no MXes exist. yes, CNAMEs are evil. > 2) will *all* SMTP relays, including S, look up the MX record for R, *NOT* > the A record? should be: MX and fall back to A if no MX exists. > 3) will *all* SMTP relays, including S, look up the A record for R, *NOT* > the MX record? if and only if there is no MX record for R. > 4) if neither 2 nor 3, is it that neither *ever* happens, or rather, that > sometimes it's done like 3 and sometimes like 2? ??? > This question strikes me as independent of other questions for which the > appropriate response is 'RTFM.' Thanks for your help, RFC2821. -- | Henning Brauer | PGP-Key: http://misc.bsws.de/hb/pubkey.asc | BS Web Services | Roedingsmarkt 14, 20459 Hamburg, DE | http://bsws.de Unix is very simple, but it takes a genius to understand the simplicity. (Dennis Ritchie)
