In these days of email and instant messaging, letter writing is becoming a lost art, and especially the formal letter. I’m pretty sure that formal letter rules are still taught in schools, but very little of it sticks. If you’re an executive or other high_ranking person within an organization, you can probably rely on your secretary or assistant to handle the niceties of letter writing, but for everyone else, knowing how to write a strong letter ourselves is important.
Quick Tip: Don't use your work email address for job searching. Use your personal email account, or set up a unique account to use just for your job hunt. Many free online email services exist, like Gmail and Yahoo mail, that you can use to set up a new email account exclusively for your job search.