The art of writing a thank you note is not a difficult one to master. Sincerity is key - so is promptness. Mention the gift/the dinner/the outing/the thing for which you are expressing thanks (hereafter "it"). Tell the recipient of the note why you liked "it" or how much you would love for "it" to happen again or how much you'll use "it". Then add a line about your relationship and why it is special. Finally, close with something genuine.
Sure, sending an email is okay to acknowledge a gift or a favor. I use email all the time to express my appreciation (I'm a sucker for a hoops and yoyo e-card). I think most people under 40 generally rely on email for most correspondence. But, there are some stalwart younger souls out there who still believe in the old fashioned pen to paper method of expressing gratitude. Maybe we have their mums to thank? Or maybe they just know...
Oh! The bonus is that the post office needs our help. :)
Try it out soon..especially on someone who would least expect it.