Dynamics 365 - Email notifications from multi-select option set

Hi,

I have a list of users in a multi-select option set with the following subset values selected
Example:
   100000001   Joe M
   100000002   Jane E

How do I retrieve their email addresses form a different look-up field
and then send an email notification to these users that are selected in my list

Any guidance is greatly appreciated

Dynamics 365 v9  on-premise