DNS / Mail problem

Joseph S D Yao jsdy at center.osis.gov
Mon Dec 16 12:32:35 UTC 2002

On Sat, Dec 14, 2002 at 06:52:36AM +0100, glederrey at swissonline.ch wrote:
> oppersdorff.net. My mail server is called cobalt.genam.ch and has the IP
> The DNS are BIND9.2.1 running on Debian Woody.
> My client wants to receive mail for "von.oppersdorff.net" and also wants
> to have a web server by that name.
> Here is the DNS configuration :
> In the zone "genam.ch" :
> cobalt IN A
> In the zone "oppersdorff.net"
> von IN CNAME cobalt.genam.ch.


> Now there are two problems (maybe unrelated). First : when this client s
> ends mail (Outlook, with her ISP's smtp server) the "From:" and
> "Reply-to:" headers get rewritten from "user at von.oppersdorff.net" to
> "user at cobalt.genam.ch". I dont have this problem with any other domain

ISTM that this may be a problem with your sendmail.cf configuration;
that is, the domain "von.oppersdorff.net" may not be in a config file
that the others are in; alternately, you may not have re-started
'sendmail' since adding the domain to all files.

OR, and this may be more likely; I think I've seen incorrectly (i.e.,
normally) configured MS mail systems do this - it may NOT be adding the
domain "@von.oppersdorff.net" to mail that it sends you!  I.e., you are
getting it a "From: user".  And, naturally, you add the

> that I host, but those domains have an MX record, and not a CNAME ; you
> cant have both an MX an d a CNAME for the same name, that is the
> following is wrong :
> von IN CNAME cobalt.genam.ch.
> von IN MX 0 cobalt.genam.ch.

Quite right.  The first would have to be an "A" record.  However, it
sounds like you DO need an MX record.  This IS a separate problem, you
were right about that, as well.  One has to do with sending; the other
(MX) with receiving e-mail.

> The question being : how can I avoid this header rewrite ?
> The next problem is that with this configuration, I need to have the
> same host for the mail and for the web (Cant have both MX and CNAME). Is
> there a better solution ?
> I can declare von.oppersdorff.net as an A record, but that doesnt seems
> "clean", if the web host moves, then I have to edit all DNS zones, and
> not only the "main" one.
> I am probably missing something, or I have some of the concepts wrong.

No, you have it right.  You could declare "www.von.oppersdorff.net" as
a CNAME record; or you could declare "von.oppersdorff.net" as an A
record.  Not as clean as one might like; but necessary by the rules.

Joe Yao				jsdy at center.osis.gov - Joseph S. D. Yao
OSIS Center Systems Support					EMT-B
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