There is no copyright protection for ideas or concepts as such.
It is only when those ideas become available in physical form i.e. as a literary work, that they are afforded copyright protection.
Copyright protection applies to all original literary works.
The term literary work means any work, other than a dramatic or musical work which is written, spoken or sung, and includes tables or compilations and computer programs and letters.
The author of the letter is normally the first owner of copyright in their literary work.
Copyright lasts for the life of the author plus 70 years.
When the author of the letter dies, copyright (like other forms of property) pass with the author’s estate to his/her heirs and beneficiaries.
As letters are normally sent by the author to a third party, the owner of the physical object i.e. the letter, may not be the copyright owner.
Where the owner of the letter is not the copyright owner, they must first seek permission from the copyright owner before reproducing the letter. However, copyright does not prevent the recipient of a letter from showing the original letter to another third party as this does not involve reproduction.