Well, for starters, thank letters have now become thank you emails; and yes, you do need to send them after every interview. It's not required, it's just a best practice and one worth getting in the habit of doing.
These emails don't need to be long, in fact, short and casual is best. Keep it brief, remind them of your conversation and let them know how much you'd love the opportunity to work for such an amazing company.
Here's what your thank you email should include:
Subject line: Thank you or Thank you for your time or Great meeting you or Great Speaking with you
How to start your email: This should start with hello or hi and be personalized greeting. (i.e. Hello Jessica or Hi Jessica)
Then what? State that it was a pleasure speaking (or meeting) with the interviewer. Mention one (or two) things that you enjoyed learning from the interviewer about the company or the position.
Reaffirm your interest in the position:
Tell the interviewer how excited you are about the position now that you've spoken with them.
Let them know they can contact you at any time to speak further.
Tell them your excited about the opportunity to work with such an amazing company or organization.
Tell them that after meeting with them you feel more confident that you can perform well in the role and tell them why.
How to end your email:
Say "thanks again" and I look forward to the possibility of future endeavors or I hope to hear from you soon.
End your email with "Kind regards" or "Best regards" followed by your name.
Thank you letter follow-ups go a long way to getting you hired. This is one step you don't want to forget.
Thank You Letter FAQs:
Q: When should I send my thank you email?
A: Thank you emails should be sent within 24-hours of your interview. It's best to wait at least 2 hours before sending, but not longer than 24.
Q: Do I need to send thank you letters after video interviews?
A: Yes, just because you didn't physically meet in person doesn't mean you don't send a thank you email. That person's opinion of you matters and can be the difference between you getting a job offer or not.
Q: Do I need to resend my resume in the thank you email?
A: No, they already have all of your information on file, so no need to reattach or resend your resume.