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 mail.linweb-enl-2.simpledns.xyz is not the root of its zone.
Instead, try zone transfer on linweb-enl-2.simpledns.xyz .
Instead, try zone transfer on linweb-enl-2.simpledns.xyz .