They copied a piece of my code (yes, it's sad that it was done without contacting me) and released their own installation script for DA: http://www.afterlogic.com/wiki/Install_on_DirectAdmin_(WebMail_Lite_6_PHP)
Forbidden
You don't have permission to access /afterlogic/ on this server.
[root@srv html]# ls -n
total 24
lrwxrwxrwx 1 500 500 29 Mar 25 13:27 afterlogic -> afterlogic-webmail-lite-5.1.4
dr-x------ 16 500 500 4096 Mar 25 13:27 afterlogic-webmail-lite-5.1.4
-rw-r--r-- 1 500 500 44 Mar 24 13:40 index.html
lrwxrwxrwx 1 500 500 47 Mar 24 22:59 phpMyAdmin -> /var/www/html/phpMyAdmin-3.4.10.1-all-languages
drwxr-xr-x 10 500 500 4096 Mar 24 22:59 phpMyAdmin-3.4.10.1-all-languages
-rwxr-xr-x 1 500 500 68 Mar 24 13:58 redirect.php
lrwxrwxrwx 1 500 500 19 Mar 24 22:59 roundcube -> roundcubemail-0.7.2
drwxr-xr-x 10 500 500 4096 Mar 24 22:59 roundcubemail-0.7.2
lrwxrwxrwx 1 500 500 19 Mar 24 23:00 squirrelmail -> squirrelmail-1.4.22
drwxr-xr-x 16 500 500 4096 Mar 24 23:00 squirrelmail-1.4.22
cd /usr/local/directadmin/scripts
wget -O afterlogic.sh http://www.custombuild.eu/afterlogic-webmail-lite/afterlogic.sh
chmod 755 afterlogic.sh
./afterlogic.sh
dr-x------ 16 500 500 4096 Mar 25 13:27 afterlogic-webmail-lite-5.1.4
Check alias directives in your Apache configs. By the way what method did you use: a newer or an older one?
Have you put info@domain as username?
Regards