Apps similar to Mail by elementary (formerly Pantheon) include Thunderbird, which is free and open source. Other options are Microsoft Outlook, Evolution, Mailspring and Apple Mail. You're spoiled for choice with Email Clients like Mail by elementary (formerly Pantheon): we list more than 50 alternatives for Windows, Linux, Mac, Android and the web.
Mulberry is a powerful, easy to use electronic mail (email) and calendar program that allows you to send, access, and manage email and calendars. Mulberry also helps you manage other related information, such as contact information.
United States
Nylas Mail Lives is a fork of Nylas Mail that fixes many longstanding issues, improves the client experience, and is committed to publish new releases.
GyazMail is a email client software for Mac OS X, based on Cocoa framework, simple, easy-to-use with many features.
Japan
Koma-Mail is an email client which is comfortable and has very handy functions. It does not need an installation, so that you can run Koma-Mail from your flash drive but, of course, also on your desktop.
Germany
EU
GermanyEU
EmailTray is a smart email client and an email notifier for POP3 and IMAP email accounts, including Gmail, Hotmail, Yahoo mail and AOL. EmailTray intelligently ranks messages, prioritizes them into 4 Inboxes and alerts you only to the most important.
TrulyMail is an email client and a private messaging system, very feature rich (voice recording, script blocking, etc.).
United States
ProfiMail is a powerful email client for mobile phones. It allows you to read your mail on the go, and send text with attachments directly from your phone. Send photos, recorded sound or simply text messages to friends, from anywhere.
Features:
SlovakiaEU
SolMail is a powerful e-mail client that helps you to manage all of your e-mail accounts & messages in one app!
South Korea
MailCode is a desktop mail client for people whose mailbox stopped being an inbox years ago and became an archive. It keeps every message on your own machine, indexes all of it, and answers a search.
Türkiye
yMail2 is a standalone email client for Windows (and Linux), available for free since 2003. Now with SSL support included so you can use it with Gmail and Hotmail POP3 and SMTP accounts.
Australia
