I have a small virtual server hosted by my provider and there I have configured a relatively simple combination of postfix, dovecot and roundcubemail (backed by nginx) that works OK. I wanted to add support for SPF and DKIM. To do that I have to add a few TXT fields to the domain configuration (I've configured it successfully on another root server hosted elsewhere, so I know how it goes).
The problem is, this hosting provider does not have a decent domain control - all I can do is add and remove subdomains, there is no possibility to add custom DNS records. So, the solution is to configure my own instance of bind and add those records locally. I have some experience with bind in a LAN, but I have never configured an additional NS for a domain already described by other public name servers and therein lies my question:
- Do I have to define only additional records as slave zone and use provider's NS servers as forwarders, or do I have to "repeat" all MX and A records already defined for existing subdomains at provider's NS?
- Since this is going to work in synchronization with provider's NS, is there anything I should watch for, like refresh, expiry or even iptables configuration?