If you receive an email soon after applying for a job letting you know that your application has been unsuccessful, then the reason will likely be that your resume does not demonstrate enough skills or experience to meet the requirements of the role. For example, one of our consultants recently advertised an accounting role where a key requirement was the ability to speak Romanian. It was very clear in the text of the ad that this was a prerequisite for the role.
The first six applications failed to show any experience in this area. You have to READ the whole job ad before applying. If you choose to apply for a role where you know you do not have the skills or you submit a resume that fails to demonstrate any experience that meets the requirements, please do not be offended when you receive an email to say you have been unsuccessful. It's as simple as that. Good luck in your job search!