Privacy focused email service Tutanota is working on a desktop email client. Check out the details.
A featureful native Linux email client that allows you to access Microsoft Exchange Server on Linux. Read and find what makes Hiri an awesome email client for Linux users.
Have a look at ProtonMail, a secure, privacy-focused email provider that you can use as an alternative to Gmail.
When we talk of email clients for Linux, generally the name of Thunderbird, Geary and Evolution come to our mind. To challenge the authority of these big players, a new open source email client is entering the market.