Email Explained: First technology principles.
Email is Good: A site about email productivity.
Email is not Dead: Email facts updated monthly.
Fastmail’s Blog: Good general email knowledge.
ProtonMail’s Blog: News from a pro-privacy email service.
Tutanota’s Blog: Privacy-centric email provider’s blog covering their product and privacy issues.
Use Plain Text Email: Setting up your mail client to send emails in plain text.