An exercise

We have to write a letter in which we reply unfavorably to an application letter.

I would like to thank you for your interest in our company.

We had read your CV with attention but, unfornatunately, your application for the post of Junior Marketing Manager cannot receive a positive answer. was not accepted.

english speakers would understand that phrase, but this correction makes it sound more native.

You have a lot of skills for the post, but we had had to considered your lack of experience in marketing.

I We hope you will find soon a post in what you are looking for with another company.

Dear Ms. Hewitt,

I would like to thank you for your interest in our company.

We had read your CV with attention but, unfornatunately, your application for the post of Junior Marketing Manager cannot receive a positive answer. [Alternative: "... unfortunately, we cannot give your application a positive response."]

"We have read..." is also possible; "We had read..." is incorrect.
The indirectness of your version is good; business letters are really like that, as if the people writing them were not really taking responsibility for what they're saying. "... cannot receive a positive answer/response" may be just a little bit too indirect, though; it makes it sound as if forces of nature are preventing this. :-)

You have many skills for the post, but we had had to considered your lack of experience in marketing. [Alternative: "... but your lack of experience in marketing was the deciding factor."]

The phrase "a lot of" is a bit informal; "many" might be better.

I hope you will soon find a suitable post with another company. [Alternative: We wish you success in finding a suitable post with another company.]

My text is rather short but let's leave it at that for now.