I refer to your letter / email of (date). I / We appreciate your interest in our company. I regret to inform you that at the present time we have no vacancies.
We would, however, encourage you to regularly check our website (insert website link) for future job and career opportunities. Your personal interest has been noted and will receive due consideration in your future applications.
(In lieu of second paragraph)
Unfortunately your qualifications / experience / are insufficient for employment as a (insert generic term for jobs referred to by correspondent) with our firm.
We require (brief but clear list of basic requirements in bullet points)
If you'd like to discuss these issues, please call (contact person, direct phone) and we may be able to advise you further in terms of career requirements.