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 postal._domainkey.rp.postal.arcatest.ch.arcatest.ch is not the root of its zone.
Instead, try zone transfer on arcatest.ch .
Instead, try zone transfer on arcatest.ch .