reverse proxy dns configuration

[cybermass]

Hi. I am looking to deploy nginx on a proxy server. The real backend is
located in a remoate geographic location and has apache, mysql, dovecot and
postfix services supporting an IMAP mail-server. I am a bit confused on how
DNS is to be setup on both the proxy and the backend server. I am assuming
that I define the nameservers in the registrar for the proxies (I will have
two; one as a failover). I am also assuming that on the proxy itself, bind
is installed of course and the MX is defined as mail.example.com for
example. I am aware that in the nginx.conf, I define the mail directive as
follows:

`mail {
server_name mail.example.com;
...
}`

Basically, I read that on the physical proxy box, the hostname can be
ns1.example.com (as long as it matches what is defined in the registrar),
but having listed mail.example.com in nginx.com means that it will be our
single point for reference for all our users looking to authenticate and use
the IMAP service. 

If I am correct so far, I would then like to know how bind is to be
configured on the real backend. Should the hostname also be
mail.example.com? I would assume that it couldn't hurt since the world is
not aware of this backend machine so pinging by hostname would not resolve
THIS box but rather the proxy box. So I am assuming the authoritative DNS
config (including the reverse DNS) is to be setup entirely on the proxy box,
leaving the real backend as just a hostname and using proxy_pass
http://physical.ip.address.

Any help would be appreciated. Thanks.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,249135,249135#msg-249135