Teaches you all the random junk that comes along with owning property and managing tenants! 

Posting notice that you are attempting to contact them (or at least sending certified mail) will at least show that you are making an effort if the tenant would later take you to court over unfulfilled repairs. 

He ended up at the UPS store (where all our mail goes) and they had to call the police.

(We would have previously updated the mailing address for the loan so the check comes to us, not the borrower!)

She sold it to us at a significant discount due to years of deferred maintenance—broken doors, heaps of junk, and more.

Notice may be given by: (A) regular mail; (B) certified mail, return receipt requested; (C) personal delivery to any resident; (D) personal delivery at the property to any occupant over 16 years old; (E) electronic mail delivery to the email address used by the Tenant to submit the lease application.

You don't know the law, you don't know how to handle difficult tenants, and you aren't local to work on it.This is what Ohio law says: “The tenant shall not unreasonably withhold consent for the landlord to enter into the dwelling unit in order to inspect the premises, make ordinary, necessary, or agreed repairs, decorations, alterations, or improvements, deliver parcels that are too large for the tenant’s mail facilities, supply necessary or agreed services, or exhibit the dwelling unit to prospective or actual purchasers, mortgagees, tenants, workmen, or contractors.”I would give the tenant a short, direct warning that they have 72 hours to coordinate with the vendor and set a schedule for repairs.

I recently started a direct mail campaign and am prepping for my second month's mailer.

An awesome view, creek side, lake side, etc.Loading up the property with a bunch of junk you can get a Lowe's won't get it done.  

The stuff that sits tends to be over priced junk in junk areas, or that have some issues with the listing, curb offers or what have you.