Hi @ Sara2018,
Could you please share a full screenshot of the configuration of your flow?
What is the trigger in your flow? Is it when an item is created?
I have made a test on my side to create a flow to send an email when an item is created, the trigger of the flow is when an item is created, and the flow would always be triggered to send the email when an item is created even if when one or more field is missed to fill out.
Please share more details about your flow and your scenes so we could provide a proper workaround for you.
Regards,
Alice Zhang