Instead of going to an InfoPass appointment in person at a local field office, you may now receive the stamp by mail. The ADIT stamp, also known as the I-551 stamp, is placed on your passport and serves as temporary evidence of lawful permanent status while your I-90, N-400, or I-751 is pending.
Not sure if it’s widely needed now, given the new receipt notices that offer longer extensions. Update: USCIS Extends Green Card Validity for 48 Months for Conditional Permanent Residents with a Pending Form I-751 or Form I-829
In the past, applicants would need to call USCIS Contact Center, wait for them to call back (sometimes at odd hours), set up the appointment, and then appear in person at a local field office. Due to complexities in this sequence of events, delays were expected.
Under the new procedure, applicants would still need to call, and the officer will determine if an in-person InfoPass appointment is needed or if USCIS can mail the ADIT stamp to the applicant.
Note this mail delivery process only applies to applicants of I-90, N-400, and I-751. I-829 applicants will need to appear in person.
Lastly, you may still be requested to appear in person if no useable biometrics on file.