Mail routing

[Sears, Robert]

Hello all,

 I am not sure if this is DNS related or mail relay related--

   My domain is nlmoc.navy.mil. When I send out email the mail relay name is
tacked onto the address so the receiver gets sears at nlmoc1.nlmoc.navy.mil
instead of just sears at nlmoc.navy.mil. Is there a way to keep the relay name
out of the address? Also if I resolve other domains (nlmod-oceana.navy.mil),
and their mail, can I keep their domain name in their email address without
tacking on the nlmoc1 relay?

thanks