This is what I use for my main domain on Ubuntu 14.04 and it works just fine:
(Change domain.com with your own)
Also, do not forget to add a CNAME record for webmail both in Sentora and you registrar (depending on your setup.)
Code:
</VirtualHost>
# Configuration for WebMail - webmail.yoursite.tld
<VirtualHost *:80>
ServerAdmin webmaster@domain.com
DocumentRoot "/etc/sentora/panel/etc/apps/webmail/"
ServerName webmail.domain.com
AddType application/x-httpd-php .php3 .php
<Directory />
Options +FollowSymLinks -Indexes
AllowOverride All
Require all granted
</Directory>
Also, do not forget to add a CNAME record for webmail both in Sentora and you registrar (depending on your setup.)