You Are Told "Never Use I"while Writing a Business Message

You are told "Never use I"while writing a business message. Is this good advice?

A) No, because there is no grammatical rule that states you cannot use I in a message.
B) No, because I is absolutely necessary when using third-person point of view.
C) Yes, because you-attitude forbids the use of I in a message.
D) Yes, because I is redundant-your reader need only look at the signature block to realize that you are the author of what's on the page.
E) None of the above.