Roundcube Webmail under login screen can be replaced by updating
parameter product_name in Roundcube config file.skin_logo in Roundcube config
file$config['product_name'] = 'My Company Name';
$config['skin_logo'] = '...'; // Please read the comment lines in
// /opt/www/roundcubemail/config/defaults.inc.php
// for more details
You can set custom logo image displayed on the login page of SOGo by replacing
file sogo-logo.png:
/usr/lib64/GNUstep/SOGo/WebServerResources/img/sogo-logo.png/usr/lib/GNUstep/SOGo/WebServerResources/img/sogo-logo.png/usr/local/GNUstep/Local/Library/SOGo/WebServerResources/img/sogo-logo.png./usr/local/lib/GNUstep/SOGo/WebServerResources/img/sogo-logo.png.