Solution: Roundcube Error 500 on Ubuntu 13.10
30. December 2013
Today I tried to install roundcube several times on my new server. I could connect to my imap mail accounts with thunderbird from home but not with roundcube on the server. After some time i found the problem: php5-mcrypt is not installed properly and causes roundcube to abort. I noticed this several weeks ago because phpmyadmin was also complaining about mcrypt not being installed altough dpkg -l said otherwise.
The solution is to fix a missing symbolic link as pointed out in this Stackoverflow question.
sudo ln -s /etc/php5/conf.d/mcrypt.ini /etc/php5/mods-available sudo php5enmod mcrypt sudo service apache2 restart