“Thank you” came, in most people’s personal lexicons, right after “please”. (Around the toddler stage. Note: Individual parenting may differ.)
Even so, it can be surprisingly difficult to get this just right. You don’t want to be too effusive. Yet an email falls far short of what is called for. Our first piece of advice is get onto it right away. Maybe even be so daring as to plan in advance. (There’s nothing worse than that “I should’ve done this sooner” feeling.) Never mind, gentle gifter, help is at hand, with a range that would make even your parents proud of your good manners.