Sending mail to a different host

[Rick Kossoris]

Hi.
I have 2 domains and 1 name server.  I will call them a.com and b.com for
this post.  I have the DNS setup for both hosts but I want the mail from
b.com to go to a.com.  I have changed the mx record for b.com to the same as
a.com and set the "IN  A" to the ip address of a.com, but I am not sure what
else I need to do.

Any help would be greatly appreciated!

Capd1