We have launched a mail cluster system for about 20,000 customers with Roundcube as webmail client.
I want to thank all of the delevopers for the great stuff you made. Roundcube Webmail is one of the best I found, because it's fast, does not have millions of options and is very very user friendly...
It is running at the Internet Service Provider Bnet in Austria (http://www.bnet.at).
greetings,
Stefan