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
Extensible by Plugins/Extensions Built-in RSS reader Support for IMAP Multiple Account support ... SMTP integration Built-in Calendar Calendar integration Categories Customizable Delivery reports Extensible by Plugins/Extensions Extensible by Plugins/Extensions Free API Gmail integration Google Calendar integration Import from Google Reader HTML Compose Integrated Chat Integrated Password Manager Integrated Web Browser Legacy addons support Export to OPML Import feeds from OPML POP3 Support Portable Secure File Sharing Tabbed interface Support for Themes Add a feature

1836 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.

Freemium $ $ $ Mac Windows Web Android iPhone ... Android Tablet Windows Phone iPad Apple Watch Android Wear
Built-in Calendar Box.com integration Calendar integration Dropbox integration ... Email scheduling Exchange Integration Flight Status Gmail integration ICloud Integration Integrated Search Multiple Account support Night mode/Dark Theme Office 365 integration Onedrive integration Organize mails Shared calendars Signature with image Smart attachments Unified inbox Yahoo Integration Add a feature

327 Like
Zoho Mail

Zoho Mail is a webmail service built with the needs of a modern business in mind. It provides features for business users to communicate effectively while catering to...

Freemium $ $ $ Mac Windows Linux Web Android ... iPhone
Custom domain Ad-free Integrated Spam Protection Mail filtering ... POP3 Support Privacy focused SMTP integration Two factor authentication Add a feature

82 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 Integrated Email Client Multiple languages Multiple Account support Add a feature

82 Like
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 $ $ $ Mac Windows Linux Arch Linux Fedora ... Ubuntu
Multiple Account support Night mode/Dark Theme Unified inbox Customizable ... Email tracking Drag n drop Email Analytics Extensible by Plugins/Extensions Support for IMAP Support for Themes Threaded Conversations Add a feature

45 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...
- Discontinued Opera Mail is no longer updated and supported, but last version, 1.0.1044, released in February 2016, can be still downloaded from the official website.
Free Mac Windows PortableApps.com
Built-in RSS reader Integrated Spam Protection Mail filtering Message Filtering ... Portable Add a feature

96 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 Office 365 integration Convert Email to Task Add a feature

27 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...
- Discontinued On its github page it states it is archived and is no longer maintained.
Free Open Source Mac Windows Linux Self-Hosted
Extensible by Plugins/Extensions Multiple Account support Add a feature

4 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...
- 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.
Free Windows
Built-in RSS reader Multiple languages Multiple Account support POP3 Support ... Portable Support for Unicode Add a feature

4 Like
TrulyMail

TrulyMail is an email client and a private messaging system, very feature rich (voice recording, script blocking, etc.). Features: Spell checking in nine...
- Discontinued The program is no longer developed. Last version, 6.0.2, released in January 2017, can be still downloaded from SoftPedia.
Freemium Windows
Integrated Search Integrated Spam Protection Portable Text to Speech 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...
- Discontinued The project is no longer developed. Last version, 1.4, released in March 2007, can be still downloaded from SourceForge.
Free Open Source Mac Windows Linux BSD
No features added 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
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...

Commercial Windows Windows S
Support for IMAP Add a feature

0 Like