[exim] shunting off email from MX1+MX2 to third unpublished …

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Author: Dennis Chang [C]
Date:  
To: exim-users@exim.org
Subject: [exim] shunting off email from MX1+MX2 to third unpublished MX running Exim4 to filter just one user locally?
Hi, all--

I wasn't sure what search terms would find me similar questions in the
archives, and the search terms I tried netted me nothing similar, so
here goes with a new post.

We've got an interesting problem where we have two main Exchange servers
as our public-facing MX1 and MX2. There is one email address in the
domain that gets hit HARD (call it "help@???"), and we would like
to shunt off emails going to that one email address using a Cisco
Ironport and directing it to a purpose-built Exim4 server. That Exim4
server WON'T be publicly visible--i.e, it won't have an MX record in
domain.com. We absolutely don't want to run the risk of emails addressed
to other users than help@??? to reach this server.

The Exim4 server has ONLY one local user, "help" with a .forward file
with the appropriate filters in there. The filter intelligently throws
away some junk mails, parses and logs others, and forward other emails
to another address, call it "support@???". There will never be
any other mailboxes hosted on this Exim4 server--all the other email
addresses in domain.com are on the two main Exchange servers. (In other
words, we needed the processing power of LINUX and Exim4 to filter this
one mailbox, because it could not be done in Exchange or Outlook.)

Here's my question: how do I configure the Exim4 server so that it will
receive the redirected SMTP connections from the Ironport meant for
help@??? and process them LOCALLY into the help Maildir while
still being able to forward emails to support@??? (via the
"deliver support@???" filter command?

Right now, if I run a test using exim -bt help@??? directly on
the Exim4 server, it does the following:

R: dnslookup_relay_to_domains for help@???
help@???
   router = dnslookup_relay_to_domains, transport = remote_smtp
   host mx2.domain.com         [172.16.0.27] MX=200
   host mx1.domain.com         [172.16.0.26] MX=200



So it is not recognizing "help@???" as being a local address and
is then relaying it out to the remote MX1 and MX2.

I need to trap this particular address here on this Exim4 server and
only redirect other emails in the same domain (especially
support@???) out to the remote MX1 and MX2.

How do I do this?

Also, I should note that I am using Ubuntu's update-exim4.conf command
and its directives to autogenerate the Exim4 configuration files. I'll
take any and all advice that works, and if you are able to describe the
solution in update-exim4.conf terms, that would be even better.

Currently, the update-exim4.conf.conf file reads like this:

dc_eximconfig_configtype='internet'
dc_other_hostnames='cmpr01','domain.com'
dc_local_interfaces=''
dc_readhost=''
dc_relay_domains='domain.com'
dc_minimaldns='false'
dc_relay_nets=''
dc_smarthost=''
CFILEMODE='644'
dc_use_split_config='true'
dc_hide_mailname=''
dc_mailname_in_oh='true'
dc_localdelivery='maildir_home'

It does not work as I would like as it is currently configured.

I also tried

dc_other_hostnames='cmpr01'

but that did not do anything different.

Please help--thanks in advance!
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