[exim] smtp through a ssh tunnel to exim4

Hello exim users,

This is my configuration for sending mail from home.
SSH is not needed on my LAN. This works with no problem.

Oberon MUA at home ==LAN==> exim4 at home ==WAN==> ISP

This is the trial configuration for sending mail from a
remote location, most commonly from work.

Remote Oberon MUA ==ssh tunnel==> exim4 at home ==WAN==> ISP

It fails. exim4 appears to reject the ssh connection
for relaying.

Someone please tell me how to coerce exim4 into relaying
a message submitted through a ssh tunnel.

And where is the exim4 configuration stored? I have
/etc/exim4/exim4.conf.template but no
/etc/exim4/exim4.conf
.

Thanks,          ... Peter E.