USCIS just announced that a few more forms will change filing locations to lock boxes. The transition will start mid-May with the Service Centers forwarding applications to the USCIS Dallas and Phoenix Lockbox facilities for processing. Revised filing instructions will be update on the forms in June.
This time some very important forms are affected, including I-140 (Immigrant Petition for Alien Worker), I-539, (Application to Extend/Change Nonimmigrant Status – separate from the I-129), I-129F (Petition for Alien Fiancé), I-817, and I-526.
As always, it is very important to download official forms from USCIS.gov website, and always double check the editions and filing instructions before mailing an application or petition.