Have a look through the mail log? There are a number of entries with size. You'll need to take care not to double-count as the size gets reported a few times as a message passes through.

system log function ok (im using 6.x)

And if you to know how many Mb for sender it's possible?

What version of ClearOS? If you are using 6.x it is in the system log.

we used Relay Host to send email and in my log file there isn't mailfilter: successfully completed

Example Apr 6 14:58:50 comune amavis[15162]: (15162-08) ESMTP::10024 /var/lib/amavis/tmp/amavis-20200406T145434-15162: <XXXXXXXX@XXXX.COM> -> <YYYYYY@YYYYl.com> SIZE=6794 Received: from smtpout.ZZZZZ.com ([127.0.0.1]) by localhost (XXXX.COM [127.0.0.1]) (amavisd-new, port 10024) with ESMTP for <YYYYYY@YYYYl.com>; Mon, 6 Apr 2020 14:58:50 +0200 (CEST)

grep -e 'mailfilter: successfully completed.*@mydomain.co.uk.*recipients=' /var/log/maillog | awk '{print $8}' | sort | uniq -c

Substitute mydomain.co.uk for your domain.