Hello, This has been resolved. Click here for the solution. First of all: thank you for all the great community support I did get over the past years. I am running my server thanks to ISPConfig and the community since the 1st of January 2019. I started with Debian Stretch and did update to Buster after a while. I did find the courage for the upgrade from Buster to Bullseye today. I did follow the excellent documentation found here: Update the ISPConfig Perfect Server from Debian 10 to Debian 11 https://www.howtoforge.com/update-the-ispconfig-perfect-server-from-debian-10-to-debian-11/ Replacing incron with systemd https://forum.howtoforge.com/threads/replacing-incron-with-systemd.88477/ How to Upgrade from Debian 10 to Debian 11 https://www.howtoforge.com/how-to-upgrade-from-debian-10-to-debian-11/ I have a few questions for which I will start separate threads. The problem I am facing at the moment is not urgent. I would like to solve the problem within a week. The problem is that webmail (Roundcube) doesn't work anymore after the upgrade. Querying https://s1.gigabitjes.nl/webmail results in a 404 error (not found). I did find the config folder which lists the following: Code: root@s1:/etc/roundcube# ls -lahs total 120K 4.0K drwxr-xr-x 3 root root 4.0K Jan 9 2022 . 12K drwxr-xr-x 135 root root 12K Jul 21 22:24 .. 8.0K -rw-r----- 1 root root 4.1K Mar 16 2020 _20200316_config.inc.php 4.0K -rw-r--r-- 1 root root 1.3K Jan 4 2019 apache.conf 8.0K -rw-r----- 1 root www-data 4.9K Mar 16 2020 config.inc.php 4.0K -rw-r----- 1 root www-data 3.8K Jul 26 2019 config.inc.php.ucf-dist 4.0K -rw-r----- 1 root www-data 524 Jan 4 2019 debian-db.php 4.0K -rw-r--r-- 1 root root 373 Nov 24 2018 debian-db-roundcube.php 52K -rw-r--r-- 1 root root 52K Jun 9 2020 defaults.inc.php 4.0K -rw-r--r-- 1 root root 3.1K Nov 5 2018 htaccess 4.0K -rw-r--r-- 1 root root 491 Nov 24 2018 lighttpd.conf 4.0K -rw-r--r-- 1 root root 2.8K Nov 27 2016 mimetypes.php 4.0K -rw-r----- 1 root root 3.8K Jul 22 2019 _org_config.inc.php 4.0K drwxr-xr-x 22 root root 4.0K Feb 9 2020 plugins I did also notice that Roundcube seems to be disabled by the maintainer of the package (?): Code: root@s1:/# find -name roundcube -print ./var/log/roundcube ./var/lib/roundcube ./var/lib/mysql/roundcube ./var/lib/apache2/conf/disabled_by_maint/roundcube ./usr/share/roundcube ./usr/share/roundcube/vendor/roundcube ./root/.composer/cache/repo/github.com/roundcube ./etc/roundcube The file "roundcube" in the folder "/var/lib/apache2/conf/disabled_by_maint" is empty. My question is what the best way is to fix Roundcube? I can't remember when and how I did install Roundcube in the past. I have memory problems after a period of illness (I am doing well - I just can't remember well). I think I might have to follow the following tutorial - although it's for Debian 10: https://www.howtoforge.com/perfect-...g-3-1/#-installnbsproundcube-webmail-optional Suggestions for the best way to resolve this are greatly appreciated. Thanks.