DVD rent-by-mail operation Netflix may be kicking rival Blockbuster where it hurts, but all is not well with the company. According to the U.S. Postal Service, the ubiquitous red return envelopes used by Netflix, hailed for saving the company millions of dollars, are prone to jamming mail sorting machines. The USPS estimates the cost at $21 million per year. To recoup that amount, the postmen propose a 17-cent surcharge per mailer. Such a charge would cost Netflix two-thirds of its operating income and lower its monthly profit per subscriber from $1.05 to $0.35. Netflix is likely to redesign its return mailer, yet again, to mitigate the burden. A company so vulnerable to the price of postage must be thinking that video downloads are looking better and better.