Hi @Jean at Packers ,
Welcome to the Community!
Congratulations on getting everything set up! I am assuming that these newsletter preferences are selected via sign up form?
I believe then you can use a segment triggered flow.
Segment
Segments are defined by a set of conditions, and will thus grow as new people meet the conditions and shrink when certain people no longer do. Triggering a flow based on when someone new is added to a segment will allow you to ensure everyone who meets a certain set of conditions will be queued for this flow. This can be useful when you want to use multiple actions to trigger a flow. Keep in mind, however, that segment-triggered flows will only send to a person once: the first time they are added to the segment. For this reason, segment-triggered flows cannot be used to automate order-related follow-up emails or any other emails you might want someone to receive multiple times for repeat behavior. These types of flows should instead be set up using the metric trigger.
Hope this helped,
Alex