Mark Lloyd wrote:
While reading this newsgroup, I looked at the first message in each
thread (there were 54 threads containing new messages).

Of those 30 of them were spam, 100% of these came from Google Groups.
There were 24 non-spam threads, 15 of those (63%) did not come from
Google Groups.

I post sometimes through google but I think g.mail, while from google,
is just used to mask identity. My posts there do not come up as g.mail.
Spammers come here because this is a popular group.