We see one such example in Re. This once popular abbreviation for in reference to which appeared in the headings of memos is becoming less and less common. In its place we find Subject, a word which communicates the same idea more clearly since the audience needs no knowledge of what any abbreviation represents. And since clarity is the first hallmark of more effective writing, support for its use in place of Re continues to grow and grow.
So in reference to Re, use Subject. Modern audiences tend to view anything archaic as less professional. You don’t want to represent yourself or your brands with that image, so if you haven’t already made the switch, do so today. You’ll communicate your messages more effectively when you present them in ways your audience more willingly accepts.