Here's how I’ve successfully found off-market properties:Direct Mail: You can pull lists of absentee owners, tax delinquencies, probate properties, and more, and send them direct mail offering a cash sale.Driving for Dollars: This means driving through neighborhoods looking for distressed properties and either leaving a note on the door or contacting the owner.Cold Calling: Use public records or services like Prop Stream to pull lists, then contact owners directly by phone to see if they’re interested in selling.Networking with Agents: Many real estate agents work with investors and have access to off-market deals (pocket listings).

If you want to verify the mailing address and send your sellers a mail piece, this data source works great. 

Its actually called "interested party" but you need to be listed as this on their policy and they will send you mail notifications

What is the best e-mail for you?

According to the telephone operator it was snail mail only for Articles of Incorporation. 

10,000 pieces of mail every month. . .ten thousand! 

I plan on mailing the letter certified and I wanted to know do landlords also call the tenant as a courtesy to let them know about the letter. 

I do SMS, cold call, mail, online, wholesalers, etc.

Enormous mass mailings.

My partner and I found this deal through an agent that gave us a list of all the 4b2b properties in the area and we sent direct mail to every household.