Monsters fan mail never opened

[TheWolfman]

 With the historic names in monster classics, Boris, Lon, Bela, i wonder if there is any historic mail sent to these movie stars that were kept and never opened. I wondr if Sarah Karloff , or Lon's grandson, and Bela jr has any stories or even old old fan mail that just bever got read or opened? Can you imagine seeing a letter sent to Boris or Bela from the 1930's or 40's and it was never opened ?

[Monsters For Sale]

It would also be interesting to see some of the mail that they kept, because the writer touched them in some special way.

[TheWolfman]

I think seeing a letter sent to a classic monster actor that was never opened, or that was kept and still excists today would be so cool. And not only would that be cool, but trying to contact that person who sent the letter, or a family member of that sender. Would'nt that be cool if a relative of any of the great monster actors contacted you because of a letter sent decades ago?

[Fester]

Not sure what you are getting at here. If there are old letters that were never opened, what of it? being sealed and never read makes their contents unavailable.  But then -- opening and reading them would destroy their condition of being never read.

Seriously, I doubt there are many letters sent to any movie star that were never opened and read.  The movie studios (and stars' agents' offices) maintained staffs to open, read, file, and answer, fan mail.  The vast majority of fan letters were requests for photographs and autographs. And it was in the studios' best interests that as many letters and requests be answered as possible.  Back then, one did not alienate fans (and lose out on future ticket sales) by snubbing the letter writers.

Even RinTinTin, the dog that saved Warner Brothers from bankruptcy, had a staff answering fan letters.  He received and his staff answered about 10,000 letters per week.

Given the market for autographs and ephemera associated with famous stars, I'm pretty sure most sources of old letters have been picked clean, including cancelled checks and old receipts signed by celebrities.
About the only places not looted by collectors and/or dealers would be studio archives, or possibly some institution that purchased (or were gifted) the personal papers of a particular star.  If you want to find those archives, I suggest you look at the bibliographies and footnotes of any books about the actor you are interested in. Any competent historian or biographer will cite the sources of his information.