Setting up reverse DNS for a small /29 block from my hosting provider

For a small /29 block (8 IPs), your provider should typically set the PTR records on their end rather than delegating the reverse zone to you. Reverse DNS for IPv4 is managed by the organization that controls the larger IP block, which is almost always your hosting provider for a small allocation. Delegation is generally reserved for larger blocks (/24 or larger) where you'd manage the entire in-addr.arpa zone yourself. Since you're experiencing lookup failures despite adding records locally, it confirms the provider's DNS servers are still authoritative for your reverse zone.

You should provide your provider with the specific IP-to-hostname mappings. For example, for IP 192.0.2.1 pointing to mail.example.com, they should configure:

1.2.0.192.in-addr.arpa. IN PTR mail.example.com.

The underlying concept is that reverse DNS relies on the chain of authority in the DNS hierarchy, and for small subnets, the parent provider remains authoritative. Delegating such a small zone would add unnecessary complexity for both parties.