[IT-SecNots] blacklisting Mailchimp and other spam sites

[Daniel Pocock <daniel AT pocock.pro>]

More and more companies seem to be taking the email addresses of
customers and uploading them into sites like Mailchimp

Even worse, I recently observed one free software project doing the same
thing, taking all the email addresses from their mailing lists and
dropping them into Mailchimp and sending reminders about their
conference every week.

Many users simply don't have time to keep on unsubscribing from these
things and it is putting them off email.

What are the options to block all of these services, such as Mailchimp,
Constant Contact, Vision6 and keep the blacklist up to date whenever
they start using new domains in the envelope?

I already have Amavis and Spamassassin packages installed but the
default settings don't seem to be sufficient.

I hear that Mailchimp was blocked for a while, apparently it was placed
on the CASA CBL:

http://www.startupsmart.com.au/news-analysis/local/mailchimp-newsletters-hitting-internet-blocks/