I have recently switched from Roundcube to Squirrelmail - the former worked annoyingly slow for me. I only had to tweak the source code a bit to get rid of these _ugly_ iframe borders.
I don't use web interface too much though.
I don't use web interface too much though.
I don't see the web interface too often anyway.
Universities often use Squirrelmail. The most recent instance I saw was for Potsdam.