Remember - CMRRRs do not require you to get the green card back. It costs more money than if you were to use the electronic RRR. The post office will give you a receipt for the CM and you can pay 85 cents for the electronic notification.
Take the receipt, log into USPS, track the number, click on the link for them to send you an e-mail when it's delivered. You'll get an e-mail with a scan of the signature.
11/14/07 TU 567 - EQ 561 - EX 577
11/29/07 TU ??? - EQ 573 - EX ???
12/10/07 TU ??? - EQ 579 - EX ??? - 60% util - OOPS!