I used to have a rule that I'd send a handwritten thank-you note after every interview. Though I still love snail mail, I now send thank-you emails.

Jessica Liebman, the executive managing editor of Insider Inc., would agree this is a smart move. In fact, if candidates don't send her thank-you email, they're toast. Liebman won't hire them. 

No thank-you email, no offer

It's a strict rule she abides by no matter the position or how far along they are in the process. Whether it's a 30-minute phone screening or final in-person interview, Liebman will not move a candidate to the next phase of the interview process if she does not receive a thank-you email.

In a piece for Business Insider Liebman acknowledges that many don't agree with her rule. But she sticks by it. She's firm: "As a hiring manager, you should always expect a thank-you email, and you should never make an offer to someone who neglected to send one," she writes.

Why a thank-you email matters

Liebman's piece sparked some outrage on social media, so she posted a follow-up to clarify her thoughts on this. She walked back her position on not making an offer.

To be very clear: The thank-you-note strategy is a rule of thumb. It is not a rule of law or an official policy. Insider Inc. has hired -- and continues to hire -- people who have not written us thank-you notes. We extended such an offer last week, which was what gave me the idea to write the story.

It's a good practice anyway. Say you don't feel like you interviewed strongly because you were nervous or your time was cut short. A thank-you email offers an opportunity to share one more data point to build your case. Liebman says it shows that "the candidate is eager, organized, and well mannered enough to send the note."

Hit on 3 key points in your thank-you email

Liebman is a managing editor for a major publisher. Which means it's her job to edit other people's work. That makes her the perfect person to offer advice on how to write the perfect thank-you email after an interview.

You'll want to keep it short and sweet. The shorter the better, she says. She recommends you hit on three key points:

Start by saying thank you.

First thing first. Thank the interviewer taking the time to meet with you and share more about the position.

Reinforce that you want the job.

Find a tactful way to say, "I really want this job." Suzy Welch, the former editor-in-chief of Harvard Business Review agrees. It shows you're genuinely excited about the position.

Plug why you are perfect for this role.

Now that you've heard more about the role and had a discussion about it, use your thank-you email as a quick summary of what you covered in the interview. Give your interview two or three really good reasons why you are ideally suited for this job.

Looking out for red flags

Liebman believes it's a red flag when people fail to send thank-you notes. To her, it signals that you don't really want the job. When they've made an offer to candidates who didn't, they've been ghosted, the offer hasn't been accepted, or they've pulled out right before their start date. ​