You need to setup the virtualhost for apache2.
[root@ck]# cd /usr/local/directadmin/data/templates [root@ck]# cp virtual_host2.conf custom [root@ck]# cd custom
Now you can edit the new virtual_host2.conf (apache 2) file in custom folder and just add the codes to the end.
<VirtualHost |IP|:80> ServerName webmail.|DOMAIN| ServerAdmin |ADMIN| DocumentRoot /var/www/html/roundcube CustomLog /var/log/httpd/domains/|DOMAIN|.bytes bytes CustomLog /var/log/httpd/domains/|DOMAIN|.log combined ErrorLog /var/log/httpd/domains/|DOMAIN|.error.log </VirtualHost>
Simply save and exit. Then run below to rewrite the httpd.conf files.
echo "action=rewrite&value=httpd" >> /usr/local/directadmin/data/task.queue /usr/local/directadmin/dataskq d
Finally you need to setup dns part.
[root@ck]# cd /usr/local/directadmin/data/templates [root@ck]# cp dns_a.conf custom [root@ck]# cd custom [root@ck]# echo "webmail=|IP|" >> dns_a.conf
Note: Please check custom folder if there is a file with dns_a.conf name. Also dont forget that is only setup webmail A record for new domains. For existing domains, you’ll have to add manually.
Source: DirectAdmin