Show a different banner in the exim welcome headers depending on IP being connected to.

This guide is old.  You can now make use of the /etc/virtual/helo_data file for this.

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If a domain has an "owned" IP, it would be possible to also get exim to show a unique banner for that IP.
You can accomplish this by edint the /etc/exim.conf and adding the following code into the top section of the exim.conf.

smtp_banner =\
 ${if and{\
           {def:interface_address}\
           {eq{${interface_address}}{1.2.3.4}}\
         } {mail.host1.com}{mail.host2.com}} ESMTP $tod_full

In the above example, any connections to 1.2.3.4 will show mail.host1.com as the greeting hostname, whilte all other connection to port 25 will show mail.host.com.