I have been working in PR for a few years, which is quite casual. Recently I have been in contact with larger organizations, and am debating between what would be the most proper way to send a business letter. For example, I recently met a high ranking official and would like to thank him for meeting with me. Do I put the business letter on a letterhead and attach this Word doc to the email? Or is a polite email sufficient? Do people even use letterheads anymore? Can someone please advise TIA!