I think that sounds like a good idea, if you feel you have some feelings you would like to 'release.' I've written a few emails and letters to H, which haven't been sent - particularly if I have been feeling angry. It can be quite cathartic to get stuff out of your brain and onto paper without filtering it too much - just letting it all pour out.
Then, you could always keep the letter for a bit or throw it away, or just burn it and let the ash pieces just blow away..
T 13 M 7 Me 48 H 46 SS 15 BD 7.14 PA D final 5.16 (H filed)
We receive & we lose, and must try to achieve gratitude & embrace with whole hearts whatever of life that remains after the losses - Dubus