Master - WWW, MySQL, e-mail, 1st DNS
Slave - WWW, MySQl, 2nd and 3rd DNS.
DNS is pointed to slave IP from subdomain.domain.com.
When typing address on slave web server I just got this:
Webmail List
1 - Afterlogic
2 - Roundcube
3 - Squirrelmail
4 - Telaen
I use php_fpm on master server and mod_ruid2 on slave (because php_fpm doesn't work on slaves).
Both use nginxproxy + apache