16.04 - How to view output of /usr/lib/apt/apt.systemd.daily after apt-daily.service is run by systemd?

In /usr/lib/apt/apt.systemd.daily it reads that

# APT::Periodic::Verbose "0";

# - Send report mail to root

# 0: no report (or null string)

# 1: progress report (actually any string)

# 2: + command outputs (remove -qq, remove 2>/dev/null, add -
d)

# 3: + trace on

I have set

APT::Periodic::Verbose "3";

in /etc/apt/apt.conf.d/10periodic. I have set up ssmtp to be able to send mails, and it seems to work, but I don't seem to get mails about the script's output.

Mail reporting may work by cron system which was used before, but not with systemd.

The output can be seen in systemd journal

journalctl -u apt-daily.service