[exim] unrouteable mail domain

Hi,

there are some domains that are unroutable, but are legitimate and I would
like to add them to exim.conf through WHM exim configuration editor.

Since I am afraid not to mess something up and I am pretty unexperienced
with exim which is very sensitive to incorrect directives,
could anyone be kind to post me the right instructions to be able to
include such domains only to be able to send mail to them?

The domains needed are for example. *.htnet.hr, t-com.hr, hotmail.com

What would the exact syntax be? And put it where into exim.conf through
WHM? First box?

My apologies for the beginners question, I am afraid not to mess exim up.

Thanks

Boris