Interview feedback email is generally written by a human resource manager or his assistant and he or she sends this email to an applicant for letting him know that he has been selected for the next interview or test. The main intention is to let the applicant know that he has passed the initial stage of the selection process.
In the first paragraph, you should write that reason of this interview feedback email. Let the applicant know that he has passed the first interview for a specific position. Also include that you all have found the first interview of the candidate appropriate.
In the following paragraph, you should add the details of the second interview which will be more specific and will contain the questions that are more specific about the knowledge and information of specific field.
In the final paragraph, you should mention the day and time of the second interview. Also add a contact number that will help the candidate if he has any questions regarding the interview.