Post interview thank you letter question

[cwsiggy]

Is it ok to send a thank you letter or letters via e-mail in this day and age? Is this lazy? How would I even subject it so they open that e-mail - "thank you letter" seems kinda dumb. Many people don't even send them which is retarded but I was wondering if it's worse than sending them via snail mail on good stationary. BTW - if it's determined it should regular mail, should I hand write it???? Sheesh it's been a long time. I have an interview tomorrow and was kinda wondering this.