Font Size: The traditional font size for a professional letter is 12. The font should be Times New Roman or Arial. However, if you are using letterhead, the letterhead may be in different font size and style. Font Style: There is no need to use different styles within a professional letter. Use a uniform font (book print font such as Times New Roman or Arial) and avoid underlining, italicizing, or bolding. However, if you are using letterhead, the letterhead may be in a different font style.
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."