In older versions squirrelmail was available as standard webmail for free. This vanished some day. Maybe a lightwighted webmail in standard would be useful again. Who want to have more functionality can buy roundcube. Or you can consider to also add rainloop as an additional to the webapps. Then you Can delete old outdated openwebmail.
Hi Dirk. I looked at Rainloop, webmail-lite and Cypth. Rainloop looks nice, but there are a few things that turn my stomach. Installation procedure? "wget -qO- https://repository.rainloop.net/installer.php | php" Seriously? Data directory inside the webtree. A whole heap of "chmod 777" in the installer, too. They seem to have spent more time on "perfect rendering of HTML email" (uhm ... security risk?) than actually thinking about secure coding.
At the end of the day anything email related is a support issue. There will always be people that then come and say: This or that email didn't get sent correctly, didn't display right or hey, I have this rare usage case where this and that happened. That's why I'd rather not have an email client built into the GUI.