What is a person called who writes letters by profession for somebody else?

There isn't one specific word for a person who writes letters by profession for somebody else. Here are some terms that might fit depending on the context:

* Letter writer: This is a general term that could apply to someone who writes letters for any reason.

* Scribes: Historically, scribes were employed to write for others, but this term is typically associated with ancient or medieval times.

* Secretary: This is a broader term, but a secretary might be responsible for writing letters as part of their duties.

* Ghostwriter: This term is more commonly used for writing books or articles, but it could apply to someone who writes letters for others anonymously.

* Professional letter writer: This is a more specific term for someone who specializes in writing letters for others.

The most appropriate term would depend on the specific type of letter being written and the context in which it is being written.