There is an old version of Thunderbird available (called MailNews because it’s not an official Mozilla supported product, and trademark protections apply). If you use Thunderbird in Zeta, this should be pretty much the same except for the branding.
You can install and run hblock, it will set up a /etc/hosts file blocking quite a lot of things. It does 99% of the job. Web browser extensions can go a little further as they will reformat the pages a bit to not leave blank spaces where ads “should” be. And hblock probably won’t succeed with things such as Youtube crazy anti-blocker javascript.