What is the test for excluding an authenticated letter from evidence at trial?

Because the letter was authenticated and was either not hearsay or was within an exception the hearsay rule, we conclude the trial court abused its discretion by excluding the letter from evidence at trial. The remaining issue we must resolve is whether the error was prejudicial, i.e., that it resulted in a miscarriage of justice. (Evid. Code, 354.) In this context, a miscarriage of justice occurs when this court is able to say, if the evidence had been admitted, it is reasonably probable the trier of fact would have reached a result more favorable to the complaining party. (People v. Watson (1956) 46 Cal.2d 818, 836.)