Didn't work
File was empty after logrotate.
47 6 * * 7 root test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )
so logrotate should be 6:47 on sunday
syslog.1 ends like this:
Oct 29 06:26:17 mail postfix/qmgr[11528]: 6FF481A0898: removed
Oct 29 06:26:17 mail postfix/qmgr[11528]: 95ED31A0808: removed
Oct 29 06:26:17 mail freshclam[1122]: Received signal: re-opening log file
Oct 29 06:26:17 mail freshclam[1122]: ClamAV update process started at Sun Oct 29 06:26:17 2017
Oct 29 06:26:17 mail freshclam[1122]: main.cvd is up to date (version: 58, sigs: 4566249, f-level: 60, builder: sigmgr)
Oct 29 06:26:17 mail freshclam[1122]: daily.cld is up to date (version: 23997, sigs: 1765803, f-level: 63, builder: neo)
Oct 29 06:26:17 mail freshclam[1122]: bytecode.cld is up to date (version: 313, sigs: 73, f-level: 63, builder: neo)
Oct 28 06:26:15 mail rsyslogd: message repeated 5 times: [ [origin software="rsyslogd" swVersion="8.16.0" x-pid="21914" x-info="http://www.rsyslog.com"] rsyslogd was HUPed]
Oct 29 06:26:17 mail rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="21914" x-info="http://www.rsyslog.com"] exiting on signal 15.
Oct 29 06:26:17 mail rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="29369" x-info="http://www.rsyslog.com"] start
Oct 29 06:26:17 mail rsyslogd: rsyslogd's groupid changed to 108
Oct 29 06:26:17 mail rsyslogd: rsyslogd's userid changed to 104
Oct 29 06:26:17 mail systemd[1]: Stopping System Logging Service...
Oct 29 06:26:17 mail systemd[1]: Stopped System Logging Service.
Oct 29 06:26:17 mail systemd[1]: Starting System Logging Service...
Oct 29 06:26:17 mail systemd[1]: Started System Logging Service.
Oct 29 06:26:17 mail rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="29369" x-info="http://www.rsyslog.com"] exiting on signal 15.
Oct 29 06:26:17 mail rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="29385" x-info="http://www.rsyslog.com"] start
Oct 29 06:26:17 mail rsyslogd: rsyslogd's groupid changed to 108
Oct 29 06:26:17 mail rsyslogd: rsyslogd's userid changed to 104
Oct 29 06:26:17 mail systemd[1]: Stopping System Logging Service...
Oct 29 06:26:17 mail systemd[1]: Stopped System Logging Service.
Oct 29 06:26:17 mail systemd[1]: Starting System Logging Service...
Oct 29 06:26:17 mail systemd[1]: Started System Logging Service.
Oct 29 06:26:17 mail rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="29385" x-info="http://www.rsyslog.com"] exiting on signal 15.
Oct 29 06:26:17 mail rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="29399" x-info="http://www.rsyslog.com"] start
Oct 29 06:26:17 mail systemd[1]: Stopping System Logging Service...
Oct 29 06:26:17 mail rsyslogd: rsyslogd's groupid changed to 108
Oct 29 06:26:17 mail rsyslogd: rsyslogd's userid changed to 104
Oct 29 06:26:17 mail systemd[1]: Stopped System Logging Service.
Oct 29 06:26:17 mail systemd[1]: Starting System Logging Service...
Oct 29 06:26:17 mail systemd[1]: Started System Logging Service.
Oct 29 06:26:18 mail rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="29399" x-info="http://www.rsyslog.com"] exiting on signal 15.
Oct 29 06:26:18 mail rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="29413" x-info="http://www.rsyslog.com"] start
Oct 29 06:26:18 mail rsyslogd: rsyslogd's groupid changed to 108
Oct 29 06:26:18 mail rsyslogd: rsyslogd's userid changed to 104
Oct 29 06:26:18 mail systemd[1]: Stopping System Logging Service...
Oct 29 06:26:18 mail systemd[1]: Stopped System Logging Service.
Oct 29 06:26:18 mail systemd[1]: Starting System Logging Service...
Oct 29 06:26:18 mail systemd[1]: Started System Logging Service.
Oct 29 06:26:18 mail rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="29413" x-info="http://www.rsyslog.com"] exiting on signal 15.
Oct 29 06:26:18 mail rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="29427" x-info="http://www.rsyslog.com"] start
Oct 29 06:26:18 mail rsyslogd: rsyslogd's groupid changed to 108
Oct 29 06:26:18 mail rsyslogd: rsyslogd's userid changed to 104
Oct 29 06:26:18 mail systemd[1]: Stopping System Logging Service...
Oct 29 06:26:18 mail systemd[1]: Stopped System Logging Service.
Oct 29 06:26:18 mail systemd[1]: Starting System Logging Service...
Oct 29 06:26:18 mail systemd[1]: Started System Logging Service.
Oct 29 06:26:18 mail postfix/postscreen[11550]: CONNECT from [***]:34767 to [***]:25
Oct 29 06:26:18 mail postfix/postscreen[11550]: WHITELISTED [***]:34767
Oct 29 06:26:18 mail postfix/smtpd[29073]: connect from unknown[***]
Oct 29 06:26:18 mail postfix/smtpd[29073]: Anonymous TLS connection established from unknown[***]: TLSv1 with cipher AES128-SHA (128/128 bits)
Oct 29 06:26:18 mail postfix/smtpd[29073]: 59FF51A0BD6: client=unknown[***]
Oct 29 06:26:18 mail postfix/cleanup[29093]: 59FF51A0BD6: message-id=<***>
Oct 29 06:26:18 mail postfix/qmgr[11528]: 59FF51A0BD6: from=<>, size=31578, nrcpt=1 (queue active)
Oct 29 06:26:18 mail postfix/smtpd[29073]: disconnect from unknown[***] ehlo=2 starttls=1 mail=1 rcpt=1 data=1 quit=1 commands=7
Oct 29 06:26:18 mail rsyslogd: [origin software="rsyslogd" swVersion="8.16.0" x-pid="29427" x-info="http://www.rsyslog.com"] exiting on signal 15.
The new syslog file is empty then.