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 mail15-cac.agiloft.com is not the root of its zone.
Instead, try zone transfer on ca-central-1.compute.amazonaws.com .
Instead, try zone transfer on ca-central-1.compute.amazonaws.com .