> Can I upgrade in parallel i.e Leave the existing in place and install/test the
> latest version and put live at my leisure?
Sure
> How is that achieved?
Install new Exim to run on different port, or at different IP address and on standard port 25. Using different IP needs that existing 2.05 version should be binded to just one interface.
Port and IP to bind can be changed with: local_interfaces
local_interfaces Use: main Type: string list Default: see below
This option controls which network interfaces are used by the daemon for listening; they are also used to identify the local host when routing. Chapter 13 contains a full description of this option and the related options daemon_smtp_ports, extra_local_interfaces, hosts_treat_as_local, and tls_on_connect_ports. The default value for local_interfaces is..
http://www.exim.org/exim-html-4.66/doc/html/spec_html/ch13.html
