Re: [Exim] Relay

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Autor: Tor Slettnes
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A: Rahul
CC: exim-users
Assumpte: Re: [Exim] Relay
On Apr 8, 2004, at 03:06, Rahul wrote:

> Is it possible to have domain based relay on exim 4.20.


Yes, it is possible. Depending on what you mean, it is stupid, but
possible.

So what DO you mean by a "domain based relay"? I see two possibilities:

- Hopefully, you are asking whether it is possible to relay _incoming_
mail to a domain, then the default configuration should work fine.
Simply add the domain(s) in question to the "+relay_to_domains" domain
list. For instance, the following line (+ create the corresponding
file) in the main section:

    domainlist relay_to_domains = /etc/exim4/relay-to-domains



- If you are asking whether it is possible to relay _outgoing_ mail
from a particular domain, you'll have to do a little bit of legwork by
way of writing custom ACL conditions. Also: BE VERY CAREFUL TO NOT MAKE
YOUR SERVER AN OPEN RELAY! For instance, you should never allow the
use of the calling party's HELO greeting ($sender_helo_name) or the
MAIL FROM: address as keys, unless you can verify these. At MINIMUM,
you should lookup the sender's IP address yourself; and you need to be
able to do a two-way DNS lookup (e.g. sender IP address -> host name;
host name -> IP address). Otherwise, a would-be-proxy-hijacker with
control of a rDNS zone could easily point an IP address to an
"authorized" domain name.

Since your question is really vague, there is not really any way to
help you further, until you state a little bit more clearly what you
want to do.

-tor