Regarding sending letter by mail to neighbors or landlord for matters of discussion

[David Luu]

Should you send it as certified mail first or as regular mail (with tracking or not), and then if no response resend as certified mail?

This is new to me, and it occurred to me, reading online, that recipient might be wary or suspicious to sign for certified mail, so I was wondering is that better sent first or as a second attempt if no response from recipient?

Would it be worse sending it first, as it alarms the recipient and they may refuse accepting the mail, and then if you send as regular mail later, they'll just throw it away without looking at it? Although if you send as regular mail first, also not sure if they'll look at it anyways.

What's the common practice for this type of communication for trying to contact neighbor or some property owner when you're not physically there to pay a visit?