It arrived 2 days later after uscis sent the email. And yes USPS is the informed delivery. They will make you sign once they give you the mail. So look out for them. And I got all my docs on the same day! They just attach it together.Great news!! After all the stress and wait, it certainly must have felt like a huge relief. Can you let us know when the approval arrives, whether it shows up in usps informed delivery? Does it require your signature? Hope you get all docs soon!