I've never understood why the Italian Registration Authority has so
restrictive parameters for DNS registrations. 
I've some domains that I manage all with my DNS, DNS that are managed by
a (wonderful) hosting provider located in the USA. In these days I'm trying to
place also my .IT domain under the control of these DNS but Italian requirements
are too much restrictive and the association is impossible.
For the Italian Registration Authority, the primary DNS must have the SOA
record configured with these parameters:
- "refresh period" >= 86400
- "retry interval" >= 1800
- "expire time" >= 604800
But the DNS around the world have not always this configuration... So, the
result? For the moment I can't use my DNS to manage my .IT domain. Terrible!
Now I'm trying a second chance... using the domain name registrar DNS as
autoritative and point their A record to my personal DNS. I hope it will
work.