So I had to mail a copy of my green card to MIT and I mailed it 3 days before the Nov 1 due date. It says on their portal that “Application Tracking allows you to see which pieces of your application have been received and processed by the Office of Admissions. Please note: close to our deadlines, allow two to three weeks for delivery and data entry of application pieces that were submitted by mail.” So I think this means that from the time if gets there, it will take 2-3 weeks to get sorted to Admissions. Will this affect my admission?
You should be fine as long as the envelope is postmarked by Nov. 1. Did you mail it from within the US? But if you want to sleep better, fax (yes, a fax) it as well and keep a copy of the confirmation from fax machine. Their fax number is: 617-687-9184. Hope that helps.