What is the proper way to deal with the security dep notice if no forwarding address?

[Mary Jay]

The tenant broke the lease and moved out and left a mess

I sent the message that the secutity deposit is not enough to cover the expenses after the tenant moved out to the last known address of the tenant (which is my rental house)

A friend went to get the mail and its sitting there in the mail box.

So, the tenant has not left any forwarding addresses and has not forwarded the mail.

What should my friend do with that mail? Leave it there? But then the new tenant probably will throw it away.

Should the friend take it to the Post office and let them know to send it back to me? Or what is the proper way to deal with it?

I need it back in case i have to go to court and if the tenant decides to take me to court if they disagree with me on non returning the security deposit