Alternatives to K-9 Mail for Windows with any license

Thunderbird

Thunderbird is a free, open source, cross-platform e-mail, news and instant messaging client. The project strategy is modeled after Mozilla Firefox.

Free Open Source Mac Windows Linux BSD PortableApps.com ... Haiku
Built-in RSS reader Extensible by Plugins/Extensions Extensible by Plugins/Extensions Built-in Calendar ... Calendar integration Categories Customizable Extensible by Plugins/Extensions Free API Gmail integration Google Calendar integration Import from Google Reader Support for IMAP Integrated Chat Integrated Web Browser Multiple Account support Export to OPML Import feeds from OPML POP3 Support Portable SMTP integration Tabbed interface Support for Themes Add a feature

1757 Like
Microsoft Office Outlook

Part of the Microsoft Office Suite, Outlook is a personal information manager that lets you manage your e-mail, calendar, contacts, and tasks.

Commercial Mac OS X Windows Web Android iPhone ... Android Tablet Windows Phone iPad Apple Watch Android Wear
Built-in Calendar Dark theme Signature with image Add a feature

311 Like
Claws Mail

Claws Mail is an email client (and news reader), based on GTK+, featuring Quick response Graceful, and sophisticated interface Easy configuration...

Free Open Source Windows Linux BSD
Lightweight Built-in RSS reader Content Filtering Customizable ... Extensible by Plugins/Extensions Support for IMAP Multiple languages Multiple Account support Add a feature

76 Like
Opera Mail

Opera Mail powerfully organizes, indexes, and sorts your messages. It has spam filtering (both automated and Bayesian), supports POP3 and IMAP, newsgroups as well as...

Free Mac OS X Windows PortableApps.com
Built-in RSS reader Integrated Spam Protection Message Filtering Portable Add a feature

96 Like
- Discontinued Opera Mail seems to be no longer updated, but you can still download it from: http://www.opera.com/computer/mail
Mailspring

Boost your productivity and send better email with Mailspring, a beautiful, fast email client for Mac, Windows, and Linux. Mailspring is free to use and an optional pro...

Freemium $ $ $ Open Source Mac OS X Windows Linux Arch Linux Fedora ... Ubuntu
Dark theme Multiple Account support Email tracking Sync Contacts ... Conversation view Customizable Drag n drop Email Analytics Email tracking & analytics Extensible by Plugins/Extensions Support for IMAP Support for Themes Unified inbox Add a feature

26 Like
Newton Mail

Newton is a fully featured mail client available for Android, iOS, macOS and Windows. Works for watch too. It's based on cloud so you can connect it to any account...

Commercial Mac OS X Windows Android iPhone Windows RT ... Android Tablet iPad Apple Watch Android Wear
Sync between devices Combined email cloud syncing Conversation view Focused Inbox ... Multiple languages Real-time pushing Salesforce integration Add a feature

39 Like
Nylas Mail Lives

Nylas Mail Lives is a fork of Nylas Mail that fixes many longstanding issues, improves the client experience, and is committed to...

Free Open Source Mac Windows Linux Self-Hosted
Extensible by Plugins/Extensions Multiple Account support Add a feature

3 Like
Hiri

Fast, good looking email client. Lighter than MS Outlook with some unique and clever features. Works ONLY with Outlook / Exchange.

Commercial $ $ $ Mac Windows Linux
Calendar integration Convert Email to Task Office 365 integration Add a feature

15 Like
Koma-Mail

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...

Free Windows
Built-in RSS reader Multiple languages Multiple Account support POP3 Support ... Portable Support for Unicode Add a feature

4 Like
- Discontinued Development of KOMA Code apps stopped in January 2017. Last version of Koma-Mail, 3.83, released in March 2012, can be still downloaded from the official website.
TrulyMail

TrulyMail is an email client and a private messaging system, very feature rich (voice recording, script blocking, etc.). Features: Spell checking in nine...

Free Windows
Portable Add a feature

3 Like
EmailTray

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...

Free Windows Android
Support for IMAP POP3 Support Add a feature

3 Like
Columba

Columba is an email client written in Java, featuring a user-friendly graphical interface with wizards and internalionalization support. Its a powerful mail management...

Free Open Source Mac OS X Windows Linux BSD
No features added Add a feature

3 Like
- Discontinued The project is no longer developed. Last version, 1.4, released in March 2007, can be still downloaded from SourceForge.
TouchMail

Navigate messages with zooms and swipes across your messages. Turn your email into colorful, visual tiles you can explore with your fingers or mouse. Rich 3D...

Free Windows Windows RT
Support for IMAP Add a feature

0 Like