Re: [exim] using exim to relay to exchange

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Author: Jason Fisher
Date:  
To: exim-users
Subject: Re: [exim] using exim to relay to exchange
> -----Original Message-----
> From: exim-users-bounces@??? [mailto:exim-users-bounces@exim.org]
> On Behalf Of Jeff Allen
> Sent: Tuesday, February 26, 2008 12:32 PM
> To: exim-users@???
> Subject: [exim] using exim to relay to exchange
>
> I am looking for a simple way to setup an exim server to relay to our
> internal exchange servers. I have reviewed the steps to use LDAP
> although with my limited knowledge of how it works I was wondering if
> there was a way to setup a flat file that exim would check against
> before forwarding to exchange i.e. I would add
> user1.lastname@???
> and exim is now permitted to forward email to exchange for that user.
> Yes I know this sounds basic but unfortunately we do not have a
> dedicated mail admin and I am a jack of all trades here and I am
> looking
> for a solution that is easy to manage... Thanks in advance for your
> suggestions.
>
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Hi Jeff. I've been using Exim4 for a while now to relay to exchange. I
run it on Debian with split config files. In its config files,
specifically in a file called 30_exim4-config_check_rcpt there is a
section like this:

  # Verify recipients listed in local_rcpt_callout with a callout.
  # This is especially handy for forwarding MX hosts (secondary MX or
  # mail hubs) of domains that receive a lot of spam to non-existent
  # addresses.  The only way to check local parts for remote relay
  # domains is to use a callout (add /callout), but please read the
  # documentation about callouts before doing this.
  deny
    !acl = acl_whitelist_local_deny
    recipients = ${if exists{CONFDIR/local_rcpt_callout}\
                            {CONFDIR/local_rcpt_callout}\
                      {}}
    !verify = recipient/callout


I have a local_rcpt_callout file in my CONFDIR (/etc/exim4) that
contains one entry which is the domain portion of our email addresses.
I have exim4 set to relay to our exchange server and having this callout
set up causes Exim4 to query my exchange server for the local part of a
recipient email address to our domain. The other half of making this
work is to configure exchange to respond to this. By default, exchange
will say that any user is a valid user unless you tell it to do
Recipient Filtering. You do that in exchange 2003 using the Exchange
System Manager. Under Global Settings, Message Delivery Properties, on
the Recipient Filtering tab, you check the box that says "filter
recipients who are not in the Directory".

I do recommend reading exim's spec on callouts. Hope this helps.

Jason Fisher