Your letters should read as if they were written by a person, rather than by an institution. Clients are not impressed by our antiquated phrases, such as “per your request,” “pursuant to our conversation,” and “enclosed please find.” Use modern English and say “as you requested,” “as we discussed,” or “I have enclosed.” Avoid pompous phrases such as “I might add,” “it is interesting to note,” and “it should be pointed out that.” Instead of saying “The use of caution is advised,” say “Be careful.” Instead of saying “Further information will be provided to you shortly,” say “I’ll keep you informed” or “I’ll keep you posted.”
Although you should be conversational, written language should be slightly more formal than conversation. Colloquialisms and slang are out. Humor is allowed.
So do your letters sound like they were written by a real, live human being—or by an institution?