Deposit Disposition sent Certified Mail Failing...Alternatives?

[Bryan M.]

My tenants moved out of one of my rentals leaving a mess and a German Cockroach infestation. I have incurred around $6K in expenses getting the place back to normal. I have sent the Deposit Disposition with documentation of what they owe via Certified Mail w/Return Receipt. The post office has been trying for a week to get it delivered but has failed. First time the reason was, "Unable to access delivery location", second time, "Unable to deliver due to animal interference". I know I have 45 days to get them the bill which I have 10 days left. If the post office gives up and returns the DD back to me what do I do? Are there any alternatives that are accepted by courts to get it delivered? Thanks!