Tell my button to report an error if the fields are not filled out correctly

Good morning,
I would like to have an email sent to my app if all the fields are well filled out, so the button should only work when they have been completed.
How can I do?

Thanks in advance

use an if block and tell it IF all textboxes are NOT empty enable button. As for the email, I am not sure if that is doable on Thunkable X at this time.