上上周六收到移民局的RFE的信，然后上周2回复后寄出，上周四delivered,然后上周5移民局网上更新说收到的我信了，今天突然网上更新变成initial review,然后是
On February 25, 2013, the post office returned the notice we last sent you on this case I485 APPLICATION TO REGISTER PERMANENT RESIDENCE OR TO ADJUST STATUS as undeliverable. This may have serious effects on processing this case. Please call 1-800-375-5283 to update your mailing address for this notice to be re-sent.
这是怎么回事？