Para quitarlo entero
V7.2
nano -w /var/www/vhosts/webmail/horde/imp/config/conf.php
V7.4
nano -w /etc/psa-horde/imp/conf.php
buscar y cambiar:
// Should we append the contents of imp/config/trailer.txt to the end
// of every message sent?
$conf[‘msg’][‘append_trailer’] = true;
Cambiarlo a false.
Para cambiar el pie del mail
V7.2
nano -w /var/www/vhosts/webmail/horde/imp/config/trailer.txt
V7.4
nano -w /etc/psa-horde/imp/trailer.txt
Y poner el contenido que interese.