The best writers strive to achieve a style that is so clear that their messages cannot be misunderstood. One way to achieve a clear style is to minimize your use of the passive voice. Although the passive voice is sometimes necessary, often it not only makes your writing dull but also can be ambiguous or overly impersonal. Here’s an example of the same point stated in passive voice and in the active voice: PASSIVE: The net benefits of subsidiary divestiture were grossly overestimated. ACTIVE: The Global Finance Team grossly overestimated the net benefits of subsidiary divestiture.
Remember, you're hoping the person who receives your letter has no memory of your closing at all. The last thing you want is a hiring manager going into an HR meeting with your cover letter in hand, asking the team if they want to meet with "Mr. Kindest Personal Regards."