If someone took a leaked dataset, like for example the Dixons Carphone leak with 1.2 million records with personal info, then generated 1.2 million letters using the template from this repo, that would make for an interesting DoS attack.

With that in mind, a big blast is also easy to filter out.

Perhaps, instead of sending them all at once, you sent a random number from 1 to 100 per day, every day, indefinitely. No way to filter out the bogus requests, forced work for the company, and unknown consequences of having these people emailed about their private information usage. Chaotic good or chaotic evil? I have my opinion.