missing Quarantine Report for malware emails

We are a company, our customer sent an email to one of our managers.
The Astaro blocked the email cause to malware in the attachment and put it in the quarantine area.
The problem is that nobody (sender or destination) had a feedback about the quarantine action. Please note that the Astaro Quarantined Report is enabled and we usually receive it for spam notification.

We would like to change this configuration in order to have quarantined report notification also for malware blocked emails but without allow final users to release them.
Is it possible?

Looking at the ASG on-line help we found that:
"Only spam e-mails can be released from the quarantine. Messages quarantined for other reasons, for example because they contain viruses or suspicious file attachments, can only be released from the quarantine by the administrator in the Mail Manager of Astaro Security Gateway"
So we did a test.
We activated the Malware option in the Quarantine Report and, from an external email address, we sent to ourselves an email with the same malware attachment.
This time we had the feedback in the quarantined report (OK) but the final user was also able to release the message (and we don't want this).

Anybody can help us?

Thanks in advance

System info: ASG320, firmware vers. 8.302, pattern 24850