Big Help needed with MX (again)

Kevin Darcy kcd at daimlerchrysler.com
Fri Jul 6 22:07:39 UTC 2001


BCC wrote:

> Kevin Darcy wrote:
>
> > MX records just say "deliver mail for name X to server Y" (or multiple
> > MX targets, for redundancy). As for *forwarding* mail, i.e. accept mail on
> > server Y and send it to server Z, typically DNS is *not* used for that.
> > It's typically something you configure within the mail server itself, with
> > e.g. a mailertable, smarthost, nullclient, mail aliases or whatever.
> >
> > - Kevin
>
> Thanks Kevin... so in this case I could avoid DNS confusion completely?
> Simply put, if someone sends an email to bryan at nextproteins.com, it will find
> its way to the webserver, which then must send it to port 25 of the proxy
> server.

Yes, you _could_ do it that way. Mail servers should fall back to using an
A record if there are no MX records. But it's more efficient to have an
MX record, even if it points to the same host, since it saves lookups. If you
want to accept mail on the web server, of course you'll need to run a mail
server on it. Which means mixing machine functions, which can be hard to
maintain and/or lead to security problems.

I'm not sure quite sure how a "proxy server" entered the picture here. Is this
something running on the same box as the webserver? If the proxy server is a
separate box, and is accessible from the Internet, why not just point the MX
record at it and eliminate the web server from the loop entirely?


- Kevin




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