You shouldn’t need to touch the A, MX and CName records unless you are using your registrar’s nameservers (usually if you are hosting the website yourself). If you point the domain to someone else’s nameservers (such as Trap17′s) then you do not need to modify the A, MX and CName records, and doing so will have absolutely no effect.
Be very careful when altering things like this, if you were to remove the ‘www’ record for instance, your web forwarding (if set up) would fail.
‘A’ records – A records are a pointer linking a name to an IP (Internet Protocol) address.
‘CNAME’ records – ‘CNAME’ (canonical name) records are a pointer to another name already in DNS. A CNAME is always relative to the current domain unless it ends with a full stop (.), then it is known as “fully qualified”.
This is NOT web forwarding. http://www.some-url.tld/ is not a valid CNAME.
‘MX’ records – These control where your email goes. Be very careful with these, if you get this wrong you will lose email. You can’t point these at just any server, you have to have agreed this with the ISP that controls them. The ‘priority’ field in the MX records governs the order in which mail servers are tried in case one is unavailable. The lower the number, the higher the priority. An MX with a priority of ’10′ would be tried before one of ’20′. The highest priority one must be the one that ultimately accepts the mail, not one that will relay it on elsewhere.
These follow the same rules as CNAMEs regarding full qualification, and must end with a full stop if the ‘domain’ part is present, (e.g. mail.domain.com.).
Put simply, the A record holds the IP address the domain points to. The MX records list mailservers for the domain. They are used in order of lowest priority number to the greatest priority number. They are the servers which will handle emails sent to that domain. CName records create aliases, sending one subdomain to another. For example, you could forward ftp.example.com to uploads.example.com or something like that.
