K-9 Mail Alternatives

Thunderbird

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

Features:

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

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.

Features:

• Address book integration
• Built-in Calendar
• Calendar integration
• Exchange
• Box.com integration
• Contacts
• Custom rules
• 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
• Todos
• Unified inbox
• Yahoo Integration

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...

Features:

• Built-in RSS reader
• Integrated Spam Protection
• Mail filtering
• Message Filtering
• Portable

Spark

E-mail app with all the great features: swipes (long/short), snooze, add (multiple) attachments from the cloud, support for various e-mail services and more.

Features:

• Clean design
• Multiple Account support
• Sync across Devices
• Calendar integration
• Email scheduling
• Exchange
• Postpone email reception
• Smart inbox
• Snooze mail

Claws Mail

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

Features:

• Lightweight
• Built-in RSS reader
• Content Filtering
• Customizable
• Extensible by Plugins/Extensions
• Support for IMAP
• Integrated Email Client
• Multiple languages
• Multiple Account support

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...

Features:

• Unified inbox
• Multiple Account support
• Customizable
• Email tracking
• Night mode/Dark Theme
• Ad-free
• Auto update
• Beauty and fluid interface
• Built-in themes
• Linux
• Multi-platform support
• Notifications
• Sidebar
• Theme Customization
• Support for Themes
• User friendly
• Drag n drop
• Electron based
• Email Analytics
• Extensible by Plugins/Extensions
• Support for IMAP
• Snooze mail
• Threaded Conversations

Airmail

Airmail is a lightweight and lightning fast mail client for Mac. Feature list: Accounts: - Unified Inbox and folders - Multi Account with editable html...

Features:

• Clean design
• Support for IMAP
• Multiple Account support
• POP3 Support
• Customizable
• Dropbox integration
• Fullscreen support
• Lightweight
• Multiple Account support

FairEmail

FairEmail is a privacy-focused email client with a setup wizard that helpfully walks you through the steps to use it with any email provider. There are many privacy...

Features:

• Calendar integration
• Privacy focused
• Security & Privacy

BlueMail

BlueMail is a modern, mobile first, powerful Email management tool with a sleek design, unified inbox and support for all your accounts: IMAP,Exchange,POP3.

Features:

• Ad-free
• Calendar integration
• Support for IMAP
• POP3 Support
• Unified inbox

Canary Mail

Canary is an exciting new email client for Mac that offers a full set of powerful features with one key difference - your emails are not stored on a 3rd party server. ...