[Q] Where do you send I-526 based I-485 applications?
As of May 3, 2010, applicants for I-526-based I-485s must file at a lockbox address depending on where the applicant resides. See page 7 of the below link:
Therefore, do not file the I-526-based I-485 at CSC. We do not know the rationale behind such change. At any event, if you encounter any problems with lockbox receipts, you should email to: LockboxSupport@dhs.gov.