How does rDNS mapping confirm sender identity?

What it proves:

• The IP owner configured a deliberate mail server name
• There is infrastructure investment (not a random compromised machine)
• The operator expects to be identified by this hostname

What it does not prove:

• The sender is authorized to use a specific From domain (that is SPF/DKIM)
• The message content is legitimate (that is reputation)

Identity chain:

• PTR says "this IP calls itself mail.tidalmail.com"
• A record confirms "mail.tidalmail.com is this IP"
• Consistency suggests legitimate, intentional configuration.

The ship declares its name. The registry confirms that name is registered to that hull. Identity verified at the infrastructure level.