Port 53 - needed if not a nameserver?

I'm just tightening up our server a wee bit more.

I have port 53 open (TCP IN + OUT and UDP IN + OUT) (It's a web and mail server)

My server is not running BIND - we are using the Linode nameservers.

There is conflicting information on forums about whether you still need to have port 53 open on your server or not, to enable it to resolve other addresses.

Can I close 53 - or does it need to be open on any of the protocols?

Cheers