The tenant should sign and date the letter and keep a copy.The notice should be sent to the landlord, manager, or agent by certified mail (return receipt requested).

., @Jim Murray, @Bryan Otteson What I did was, I sent out a letter to all residents stating that we've changed our pet policy.

Tell him I sent ya!

When I had to cancel a lot of my reservations for my condo I sent them the letter that my HOA sent me banning short term rentals and they waived all of my cancellations for free.

Hi @Anthony Angotti, I just sent you a message.

His lease states that subletting is not allowed, but I sent an addendum allowing him to sublet to his friend.

I've even sent a list of possible properties in numerous zip codes.

They claim to be much more specific, which makes you think they are more valuable, but in the end my response rate has about the same, but with a higher cost and less mailings sent out. 

@Nick Pearson I just sent you a colleague request so I can get you my information!

In the beginning you typically want to be able to go out and look at the properties so that you can learn more and so that you can better estimate the repair costs (so that your cash buyers don't get angry at you because you sent them a bad deal).