Bug#956962: exim4: Please provide a substitution variable for 'interface'

[Christian Kastner]

Package: exim4-daemon-heavy
Version: 4.93-14
Severity: wishlist

While setting up SPF and DKIM on a host with a multi-IP setup, I noticed
that connections to the outside were made from the first IP, and not the
one I had reserved specifically for SMTP traffic (and on which exim4 is
listening). This makes SPF checks fail.

The solution was to specify the 'interface' option [1] in file
conf.d/transport/30_exim4-config_remote_smtp.

However, it would be nice to have a substitution variable for this, so
that a change to a conffile can be avoided.


(By the way, I'm a huge fan of the substitution system! It does so much,
yet requires so little work to override. It's probably my favority
config in Debian).

[1] https://www.exim.org/exim-html-current/doc/html/spec_html/ch-the_smtp_transport.html