Mailspring Alternatives

Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!

Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.

eM Client is a fully-featured email client for Windows and macOS with a clean and easy-to-use interface. eM Client also offers features for calendars, tasks, contacts, notes, and chat.

freemium

Mailbird is the best email client for Windows 7, 8 and 10

Airmail is a lightweight and lightning fast mail client for Mac.

The Power Email App for busy professionals, like you.

The Bat! is a secure desktop email client for Windows, designed to protect your correspondence against third-parties and to save your time.

Geary is an email application built for GNOME 3.

Apps/Evolution - GNOME Wiki!

Add forums and commenting to your site. Unlimited posts, users and traffic, for free. Embeddable, styleable and scriptable.

Spark helps you take your inbox under control. Instantly see what’s important and quickly clean up the rest. Spark for Teams allows you to create, discuss, and share email with your colleagues

Claws Mail is an email client (and news reader), based on GTK+, featuring Quick response

K-9 is an opensource email client making it easy to chew through large volumes of email.