Reply #46: It depends on you.

[AZCat]

The world being as it is, we all have to (at some point) accept certain sources as authorities, because we as individuals are not capable of examining all evidence first-hand either because of the limitations of our personal resources (we may not be able to test properly ourselves the properties of steel when exposed to fire) or because the evidence was only available to certain people (direct witnesses to an event, for example). Which sources are accepted is, of course, a personal decision. Some people may grant the letter-write in the OP such status, while others may not. Just because you do not decide to view the source as valid doesn't lessen the sources possible validity for other individuals, although if you have reasons for not accepting the source it would seem fair to bring those to the attention of others.