RESOLUTION
You can add your own template to /etc/mail/spamassassin/local.cf. As example use the one from /usr/share/spamassassin/10_misc.cf:
clear_report_template
report Spam detection software, running on the system "_HOSTNAME_", has
report identified this incoming email as possible spam. The original message
report has been attached to this so you can view it (if it isn't spam) or label
report similar future email. If you have any questions, see
report _CONTACTADDRESS_ for details.
report
report Content preview: _PREVIEW_
report
report Content analysis details: (_SCORE_ points, _REQD_ required)
report
report " pts rule name description"
report ---- ---------------------- --------------------------------------------------
report _SUMMARY_
Restart SpamAssassins after the changes.