held with 'invalid HTML Spam', how to determine ?

[lists at sbt.net.au]

how to tell what's causing some emails to be held (beyond the obvious...) ?

Is this from amavis, or am I wrong again..?

I have several emails 'held', looking by queue ID in mail log I see like:

==================
# grep 89FD43827EC  /var/log/maillog
Sep 25 14:00:15 postfix/smtpd[4379]: 89FD43827EC:
client=61-xxxx.static.asianet.co.th[61.xxxxx], sasl_method=PLAIN,
sasl_username=yyy-1 at tld.com.au

Sep 25 14:00:16 postfix/cleanup[2981]: 89FD43827EC:
message-id=<506127C6.5050703 at tld.com.au>

Sep 25 14:00:16 postfix/cleanup[2981]: 89FD43827EC: hold: body >
_<graph-1 at tld.com.au>_ <mailto:yyy-1 at tld.com.au>,  from
61-xxxx.static.asianet.co.th[61.xxxxxx]; from=<graph-1 at tld.com.au>
to=<rrr at tld2.com> proto=ESMTP helo=<[10.0.0.107]>: Invalid HTML Spam