The correct salutation on a cover letter should always include the word "Dear" followed by the contact person to whom the letter is addressed. This should be followed by either a comma or a colon, then a blank line and the first line of the letter.
It is important to address a person formally in a cover letter, by addressing them as Mr. or Mrs. If the person who is receiving the cover letter is a doctor, he or she should be addressed as Dr. When unsure of who is receiving the cover letter, some options include: "Dear Hiring Manager" or "Dear Sir or Madam."