To combat this, some writers implement the dreaded form letter response: "Due to the overwhelming amount of mail received," and "While I wish I could respond to each inquiry personally," and "Your paltry existence could not possibly be one iota less important to me."
Robert Heinlein (of Starship Troopers fame) has his own unique take on the form letter. It is ... super unique. Opening with the decidedly noncommittal salutation "Dear Sir/Madam/Ms./Miss," it soon launches into an extensive FAQ (minus the Q). Heinlein's check-the-answer form letter came replete with responses ranging from simple thank-yous, to obscure references, to long-forgotten publications that could only possibly have answered one ludicrously specific question.