receiving mail

[destr0]

I'm confused on the concept of recieving mail.

I have two machines set up as my little test domain.

I one host set up as mail.mydomain.com / wich runs imp

and one set up as destro.mydomain.com /

if I login to imp on mail.mydomain.com I can check my mail, and send mail to
my test address and imp will pick up the message.

if I try to use kmail on destro.mydomain.com to send a message to  "a
user"@mail.mydomain.com, imp doesn't pick the message up.

As far as I can tell it's becuase when I send mail from the machine I have
imp running on, it runs through the local host, so it routes properly, but
when I send mail from the other machine, sendmail doesn't pick it up.

What do I have to set in sendmail for it to recieve mail from other
machines?