If you're serious about sending anonymous emails and also want your email communication to remain encrypted, then your best option is using a service like ProtonMail,
MailFence, or Tutanota.
While well-known picks like the DuckDuckGo search engine,
Firefox and Tor internet browsers, and Tutanota email service are included(among many others),
the Ethical Alternatives & Resources list goes beyond just one-to-one replacements to Google, Microsoft, or Apple products.