nickE400

I received a notice from MB that the warranty on my 2016 E400 coupe is being extended to 20 years and unlimited mileage from the date it was new due to rear subframe corrosion issues.
Question - is there a history of rear subframe problems (must be), and if I wanted to monitor this occassionally where would the most likely place to observe any corrosion?
TIA

Mr. Toad

I recently received the same letter (for the same year/model), and yes, there is an entire thread here devoted to this issue.