Do not expect to win the employer when your resume and resume are common without any particularity. So, do not waste time sending imperfect resume and resume to different employers because your chance of getting to the next round is not significant at all.
Make your resume and resume differ from those of other candidates. As such, you should never start your resume with such general salutations as dear sir, or dear sir. Normally, when a company posts publicly a recruitment ad, it will surely address the name, address and contact number so as the resumes may be sent to correct address.