There would also need to be routing instructions to deliver to K1000.yourcompany.com Very Simply the host K1000.yourcompany.com must be resolvable by the DNS server that your Domino server uses. A simple test would be, can you correctly ping that name from your Domino Server?
From Domino's perspective, it is the same as delivering mail to the internet but logically what happens is it gets delivered to your local K1000 appliance.
In this way, even external users can send mail to the K1000 appliance because they still address their mail to your regular company.com address. Any mail that comes from the k1000 appliance can be set to appear to be coming from email@example.com by puttting this value (ie firstname.lastname@example.org) in the Alt. email address field for your helpdesk queue.
The prefix of the "Alt. email address" (ie helpdesk) must match the prefix of the special users' email address (ie email@example.com)