Changes since SOA version
IXFR is a zone transfer request that returns changes since a specific SOA version. Enter the SOA version to request changes since then.
Not an apex domain
The domain postmaster._at_.reliable-nets.com._forwarding_spf.reliable-nets.com is not the root of its zone.
Instead, try zone transfer on _forwarding_spf.reliable-nets.com .
Instead, try zone transfer on _forwarding_spf.reliable-nets.com .