Comment 1 for bug 191489

If the debconf options sympa/use_wwsympa is true, the postinst script for sympa will set wwsympa.fcgi suid sympa.

To use wwsympa and the soap interface, run dpkg-reconfigure sympa and enable wwsympa, fastcgi and the soap interface. If your debconf is not comfigured to display these options, you can change them using this little script (which is what I used):

cat <<EOF > /tmp/debconf.input
sympa sympa/use_wwsympa boolean true
sympa wwsympa/fastcgi boolean true
sympa sympa/use_soap boolean true
EOF
debconf-set-selections /tmp/debconf.input
aptitude reinstall sympa

This should set the correct permissions. Please note that there should only be one space between "boolean" and "true".

If anyone is interested: I learned this by reading /var/lib/dpkg/info/sympa.postinst