Good day GuyWig
As far as my knowledge goes this is not yet possible to do in K2 Five. This may be added on a later stage or be added in K2 Five (5.3) which releases soon but cannot confirm it as of yet.
I can, however, suggest that you can build a workflow that will send an email when I user is noted out of office which will entail that the email sent will be the custom one that exists on the workflow.
If this post, or any of the above post's answer your question please remember to mark it as a solution.
Thank you
Regards
Jacques.