[BlueOnyx:22442] Email for sub domains

[Colin Jack]

Bit of a noob question really but I need to set up email for a client using subdomains to send email to different servers.
Seems pretty straight forward but struggling with getting the DNS setup correctly.

So root domain is domain.com
Nameservers for root domain are ns1.domain.com and ns2.domain.com
They want email to @domain.com to go to mail1.domain.com and email to @works.domain.com to go to mail2.domain.com

I have created the necessary mx records on ns1 and ns2 for both the root and sub-domain

domain.com.        in mx 0  mail1.domain.com.
works.domain.com.        in mx 0  mail2.domain.com.

Email only goes to root domain. 
Try dig mx works.domain.com and no reply so logic says can't find zone records. :-/

So try adding sub-domain delegation to dns records:

works.domain.com.  in ns ns1.domain.com

Still doesn't work.

Maybe I need to add a glue record for ns1.domain.com? 

ns1.domain.com in a 11.12.13.14

Nope. 

Maybe set the sub-domain records up on a different server?

Any guidance much appreciated!

Colin