Apparently, it's totally legal for "businesses" like the United States Trademark Registration Office to send you letters threatening to cancel your trademark unless you pay up. The fine print says it's not a bill, disclaims being a government agency, and essentially lets the scammers escape any legal liability. But don't pay them.
You may have a keen sense of whether or not you won a Nigerian lottery or, the latest phishing scam, that your loved one got mugged in a third world country and needs a wire transfer post haste. But don't think your business is immune to these scams! It may seem like a rounding error to your business' bottom line, but every penny saved is a penny earned.
When in doubt, contact an attorney or financial professional. We're here to help.