Alternatives to Opera Mail for Linux 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.
- The addons extend Thunderbird's functionality making it by far the best email client ever made. zibusisomasuku • May 2017 • 0 agrees and 1 disagrees
Free Open Source Mac Windows Linux BSD PortableApps.com ... Haiku
Extensible by Plugins/Extensions Built-in RSS reader Built-in Calendar Calendar integration ... Categories Customizable Extensible by Plugins/Extensions Free API Gmail integration Google Calendar integration Import from Google Reader HTML Compose Support for IMAP Integrated Chat Integrated Password Manager Integrated Web Browser Legacy addons support Multiple Account support Export to OPML Import feeds from OPML POP3 Support Portable Secure File Sharing SMTP integration Tabbed interface Support for Themes Add a feature

1794 Like
Evolution

Evolution is the official personal information manager and workgroup information management tool for GNOME. It combines e-mail, calendar, address book, and task list...

Free Open Source Linux BSD S/MIME GNOME OpenPGP
Built-in RSS reader CalDAV Calendar integration CardDAV ... Encrypted email Integrated Spam Protection Multiple languages POP3 Support Add a feature

153 Like
Claws Mail

Claws Mail is an email client (and news reader), based on GTK+, featuring Quick response Graceful, and sophisticated interface Easy configuration...
- No central inbox or unread box for all mailbox accounts Guest • Oct 2017
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

77 Like
Geary

Geary is an email application built for GNOME 3. It allows you to read and send email with a simple, modern interface.

Free Open Source Linux BSD GNOME
Multiple Account support Add a feature

72 Like
Sylpheed

Sylpheed is a simple, lightweight but featureful, and easy-to-use e-mail client (mailer, MUA). Sylpheed runs on many systems such as Windows, Linux, BSD, Mac OS X and...
- No central inbox or unread box for all mailboxes in one place. Guest • Oct 2017
Free Open Source Mac Windows Linux BSD PortableApps.com
Lightweight Add a feature

51 Like
Trojitá

Trojitá, is a fast Qt IMAP e-mail client that respects open standards and facilitates modern technologies. Trojitá values vendor-neutrality that IMAP provides...

Free Open Source Windows Linux
IMAP debugging Support for IMAP QT Based Add a feature

12 Like
Pantheon Mail

Pantheon Mail is a free open source email client forked by the elementary OS community from Geary...

Free Open Source Linux elementary OS
Multiple Account support Add a feature

7 Like
Mulberry

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...
- Central inbox tells which account the email is for. Guest • Oct 2017
Free Open Source Mac Windows Linux
CalDAV POP3 Support Sync Calendars Add a feature

5 Like
- Discontinued The project is no longer developed. Last version, 4.0.8, released in February 2007, can be still downloaded from the official website.
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

23 Like
Simple Mail

Simple Mail is a mail client for Firefox. It allows you to get notified, read and write messages for multiple email accounts inside Firefox. Usage: Configure one or...

Free Mac Windows Linux Firefox
No features added Add a feature

5 Like