Obviously there is a glitch in the system.  It costs IRS postage but it shouldn't cost you time, now that we know it's happening all over the place.  Shred and move on. 

(Speaking of IRS postage, I received a letter from someone with Taxpayer Advocate Service who is obviously working from home, because it had a "Forever Stamp" on it.  IRS doesn't issue postage stamps to employees, as far as I know.  But then, I'm not sure if this wasn't a Chinese counterfeit.)