Flyer distribution issue

[Ryan Cleary]

So, my original plan was to drop "handwritten letters" off in every single mailbox of my town of 850 homes (they are all close proximity so as far as walking to each house it could be done in one or two days.  Its just an innocent letter stating I am a new agent and would love to assist you in the future etc.  

What are your thoughts since technically only the USPS workers are legally allowed to place mail in someones mailbox?  I also don't want to come across as spammy and leave them in strange places like tucked in the screen door.  I would also prefer not to actually mail them since that would involve placing the address on each envelope.

So right now my situation is that I have 850 handwritten letters (not actually hand written but you can't tell) and no way to distribute them.  Ant solutions?