My Neighbors tree is dying and hangs ominously over my backyard and shed. The tree has noticeable fungus growth and decay. A second tree that was kind of attached at the base to this tree has actually just fallen into my property (I am taking the bill for this one). While getting quotes from tree removal companies for the second tree they also mention the dying tree is probably a hazard.

I don't want to be stuck with another tree removal bill. From what I understand, notifying the neighbor is a good way to transfer liability. I don't mind doing this in person, however I would like to communicate this in a way that can be documented for future reference if needed. Is there a way to prove a specific letter has been sent to this person? or any other method?

Thanks