Dear members, Is it ok if I send this letter to request reasons of rejection after a postdoc interview?
First, I want to apologize for not replying to your previous emails sent to my Hotmail. I don't regularly use Hotmail for my important communications. Second, I would like to express my deepest gratitude for your kind feedback. However, I couldn’t understand if the rejection reason was because of something missing in my qualifications or the way I presented myself. I was extremely excited about this position, and to be honest, I was quite hopeful of getting the position. It is disappointing having years of experience I lose the chance to be part of such a great project, which I found related to my research background and interests, particularly the one out of the other four research challenges: ****
I wish all the best for you and your research group, and totally understand If you won't be able to respond to this email.

I'd strongly advise against this. First of all, they must only have the email address that you supplied to them, right? Therefore it's a bit strange to start with having to say that you "don't regularly use it for important communications." Where did they get the address from? Was it on a public website, or your CV? If they have the wrong email address, that is your responsibility, not theirs.

Secondly, if they've already provided feedback (as it sounds like they have) I would not ask for more. You only give two options for the reason why you might not have got the job (your qualifications or behaviour) and in 99% of postdoc rejections, the reason is neither: mostly we don't get the job because there was someone who was a better fit for the project. Asking them to explain why you personally weren't good enough is a little weird.

I'd say it is dangerous to say something like "to be honest, I was quite hopeful of getting the position." You were invited to interview which meant you were given a chance, along with the 4-10 other people who were probably also interviewed. The others could be coming from anywhere in the world with any set of skills or experiences. They might be very well known to the recruiters, or in the same lab, or prior collaborators. I was once in a postdoc interview where all 7 candidates had been co-supervised by the project PI or had coauthored papers with them, including myself. Therefore every person was exceptionally well-qualified for that post and there were 6 disappointed people who all thought they had a chance. I co-wrote multiple papers with the PI and I still didn't get it.

Your email comes across as if you can't understand why anyone else in the world would be chosen above you. That's not a great message to send to a research group who may have vacancies in the future. They clearly had good reasons for coming to the decisions that they did. Of course you're disappointed, as I'm sure everyone else was too. If I was in your position I would try to swallow your pride and get more experience rather than send this. "I wish all the best for you and your..." sounds like the kind of thing you might say when you were breaking up with someone you don't really want to talk to again, not when you're asking for professional feedback on a job. Others may disagree but to me it comes across as overstepping boundaries...

I suggest not to send that email and I 100% agree with glimmerbat.

Postdoc applications can be super competitive with several applicants more than qualified for the role. Sometimes you are just unlucky and email strikes a very ungrateful tone. So don't damage your career for no potential gain.

I agree with the other two. Don't send the email- they have already given you feedback.
For perspectives- When I left my last postdoc, I was asked to help with the interviews for my replacement- there was over 5 applicant for 2 roles- in which 10 were interview. You were lucky to get feedback in the first place (a lot of PIs don't bother).
Also, it's important to remember- PI usually keep the list the interview in case the person leaves after a few months- saved them re-interviewing so you don't want to have bad blood there.

It's bad not in concept but because the tone is unprofessional.

You shouldn't have given a hotmail correspondence email if you do not regularly check it. This is really bad as a starting point. I would not hire you on this basis. It shows a total lack of professionalism.

It can be worded in a professional way, but this would need reference to the original feedback. It's very much ok to ask for clarification on it, but if you slip into the space of arguing their decision that's already made or attempting to show it's a bad decision, it's futile and will look bad.

You should understand rejection from a competitive hire isn't like undergraduate study; you don't get a hire for scoring X, you get a hire for scoring higher than anyone else who applied. This is totally a shock to many students who have done well in their studies and don't understand the competitive, and random (you can't control who else applies) nature of the real world.

Learn, and move on, imo.

it could be no reason, just because other candidates have stronger CV. Also it feels wired and not polite to send such a letter, kind of saying "how dare you reject me" even you don't mean to.