Yeah, I hate that too. Why respond if you are just going to tell someone to search. At least give them a link then. I searched and didn't find any links. Maybe the poster did the same thing.
To answer the question, you can only insert tag lines on emails being sent from the webmail interface.
Here is where it is set:
/etc/e-smith/templates/home/httpd/html/horde/imp
/config/conf.php
In the file 200MessageSettings
So, I'd suggest creating a directory:
/etc/e-smith/templates-custom/home/httpd/html/ horde/imp/config/conf.php
Then copying the 200MessageSettings to this new directory, edit the file accordingly then,
/sbin/e-smith/expand-template
/home/httpd/html/horde/imp/config/conf.php
Check your conf.php to make sure your settings are correct. Then edit the file trailer.txt in
/home/httpd/html/horde/imp/config to your liking and send a test e-mail via webmail to confirm.
HTH,
JB