Also, make sure to waive the signature confirmation if mailing by USPS Express Mail. I forgot to do that in my case. USPS left a note to pick up my mail and the following day a person from USCIS picked it up from the post office. I called the local USPS office in Mesquite, TX and they told me to not worry and this is normal for them. USCIS does pick up signature confirmation mails from post office the following day. But to avoid any confusion or delays, better to waive signature confirmation.