Without knowing anything about what letters you are planning to use a fake name on, it's hard to say. You did remind me of an anecdote I posted in 2002 and I didn't have a problem with it:
Texas bank near federal correctional facility for men: Inmates (clearly with large amounts of time on their hands) would often write or call the bank concerning their accounts. They were extremely grateful for the prompt, courteous attention their phone calls and letters received from one of the bank's employees, Adelle Martin. After their release from prison, several stopped by the bank with a gift of candy or flowers for Miss Adelle. (One was hoping to take her to lunch.) Unfortunately, in each case, they learned that Ms. Martin no longer worked there and the bank had no information on how to get in touch with her.
There never was an Adelle Martin employed in the bank. However, when a letter, a call or a caller was received for her, bank employees automatically realized they were dealing with an inmate; someone with whom they might not want to develop a personal relationship; "Adelle" was a useful tool who allowed them to be at their best when dealing with their customers.
In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.