I'd be more worried about DMARC failure that's visible by Gmail users in headers:
dkim=neutral (body hash did not verify) header.i=@;
dmarc=fail (p=QUARANTINE dis=NONE) header.from=
libero.it
Inspect
libero.it's SPF and DMARC records and adjust them accordingly, so that
gnu.org servers are allowed to send mails on behalf of users @
libero.it:
DMARC records currently order Gmail (and others) to quarantine emails unless they were sent by servers in SPF records:
which seem to be some BlackBerry servers, plus those in
212.48.25.128/25 IP range.
It's possible that just adding "include:
gnu.org" to
libero.it's SPF record would be enough.