(Ted Harding) Ted.Harding@wlandres.net
However, when I send the mail out, it seems that exim4 changes the "Sender:" address to "ted@deb", "deb" being the name of my machine on my home LAN (as set in /etc/hosts), and "ted" being the user. [...] What I want to do is ensure that exim4 (aliased as 'sendmail') either does not change the "Sender:" header as it is while still in the outbox, or else sets it anyway to [...]
/etc/email-addresses defines the outgoing externally-safe address for each user in the usual debian exim4-config.
If a user is not listed in there, you're getting the default hostname (FQDN).
I don't think "deb" should be the FQDN of any machine, so there's probably some problem with /etc/hosts or /etc/hostname but setting the address in email-addresses would be OK.
If you prefer to do it with command-line options, -f might do it, but I suspect email-addresses may override it.
Hope that informs,