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 za-smtp-inbound-1.mimecast.co.ZA is not the root of its zone.
Instead, try zone transfer on mimecast.co.ZA .
Instead, try zone transfer on mimecast.co.ZA .