I think, it does well deserve to be placed Horror stories.
Consider the given server for with or without SMTP service role, this script tries to process 3000 mail commands in parallel to send the text to it's 3000 repective receipents.

Have you ever tried with valid 3000 e-mail IDs, you can feel the heat of CPU(sar 1 100)

P.S.: I did not tested it but theoritically affirmed.

Best Regards.