Security deposit itemization are mailed by USPS first class , not regular mail.

The following information was correct per USPS on Dec 7th 2013 but may change in the future .Contact USPS.COM for more details. 

Someone must be available to sign for each USPS Certified letter. If you are mailing to a residential address and no one is home, a delivery reminder slip will be left in the mailbox by the letter carrier.  This reminder informs the person a USPS Certified Mail letter is being held at the local Post Office for pick-up.  They must go to the Post Office to Sign for the letter and pick it up. If no one picks up the letter after 5 to 7 days, USPS will leave a second delivery notice.  Again the delivery slip reminder is left by the letter carrier. Finally after 5 to 7 days the final delivery attempt is made to the delivery address.  After the final notice reminder is left the letter is taken back to the Post Office and held for 5 to 7 days prior to being returned to sender with USPS proof of the various attempts of delivery and notification.

This entire time frame can take 17 to 21 days if no one claims the letter.