I thought this is easy, but apparently not. There is a custom list
called projects with a field named Notifications of type "Person or
Group". The purpose of the field is to hold the persons who should
receive the notification.

In SPD, while trying to create a workflow of sending emails, for the
To field of the message, the field of Notifications is not available
(workflow lookup ->Source (Current Item), under Field, the
notification field is not available).

How can I get the emails of the persons in the Notification field in a
SPD workflow?