Registered, certified mail to Dallas Lockbox?

[studioguitarist 5]

Hello,

I am preparing to mail my I-129F petition for K1 fiancee visa to the Dallas lockbox address. Because this address is a PO box, I am wondering if I can still mail it "certified" or "registered" with a return receipt. I worry that if I do, it might be returned to me as undelivered because there might not be someone there to actually sign for it (since it is apparently a PO box). I hate to just drop it in the mail and trust the postal service not to lose it -- I really want proof of delivery.

Thanks

[fqadri 8]

For USPS Express Mail and courier deliveries:
USCIS
Attn: I-129F
2501 South State Highway 121 Business
Suite 400
Lewisville, TX 75067

From the USCIS website: http://www.uscis.gov/i-129f