I use a new workaround now. I replaced sub do_7zip in /usr/sbin/amavisd-new
with sub from 2.11.0.
Encrypted archives are properly detected now when 7z is used and the subject is
> -----Original Message-----
> From: amavis-users [mailto:amavis-users-bounces+christian.hoyer-reuther=cac-
> chem...@amavis.org] On Behalf Of Hoyer-Reuther, Christian
> Sent: Wednesday, September 14, 2016 2:11 PM
> To: firstname.lastname@example.org
> Subject: Encrypted archives and 7z on Debian Jessie (amavis 2.10.1)
> our mailserver run amavisd-new-2.10.1 on Debian Jessie. Regarding encrypted
> archives I configured $undecipherable_subject_tag = '+++Virus scan failed+++
> ' so the recipient is notified that the archive could not be scanned.
> But when 7z or 7za is used as decoder of an encrypted archive then the
> subject is not modified.
> According to the release notes this problem seems to be fixed in amavisd-
> new-2.11.0 ("updated decoder for 7z archives to improve handling of
> encrypted content; based on a patch by Markus Benning").
> I don't know if 2.11.0 will be available on Jessie (or at least the fix for
> 7z), but for the moment I use the internal decoder for zip files as a
> workaround. Then it works and the subject is modified.