In the console, navigate to:

 /usr/share/psa-horde/config/registry.php

Edit:

Edit /usr/share/horde/config/registry.php

Find the line: 'name' => _("Horde");

and replace with:

'name' => _(preg_replace('/^webmail./', '', $GLOBALS['HTTP_SERVER_VARS']['SERVER_NAME']) ),

That should change the 'Welcome to Horde' message to 'Welcome to domain.com'

To remove (or replace) the default horde logo, edit the common-footer at /usr/share/psa-horde/templates/

To Remove/Change the Parallel's link and logo:

File: psa-horde/config/conf.php

Change:

$conf['logo']['image'] = '';
$conf['logo']['link'] = '';

Only to discover the webplasten logo found here:

Coment this line out:

File:  psa-horde/templates/portal/sidebar.inc

Also, to remove the MOTD footer or change it, its here:

File: psa-horde/config/motd.php
File: psa-horde/imp/config/motd.php

<!--
<table width="100%"><tr><td align="center"><?php echo Horde::img('horde-power1.png', _("Powered by Horde"), '', $registry->getImageDir('horde')) ?></td></tr></table>
-->