K-9 Mail Alternatives for Windows

K-9 Mail is not available for Windows but there are plenty of alternatives that runs on Windows with similar functionality. The best Windows alternative is Thunderbird, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 25 alternatives to K-9 Mail and 19 are available for Windows so hopefully you can find a suitable replacement. Other interesting Windows alternatives to K-9 Mail are Microsoft Office Outlook, Spark Mail, Mailspring and Delta Chat.

K-9 Mail alternatives are mainly Email Clients but may also be Calendar Apps or WebMail Providers. Filter by these if you want a narrower list of alternatives or looking for a specific functionality of K-9 Mail.

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K-9 Mail

291

Free • Open Source
Email Client

Android
Android Tablet
F-Droid

K-9 is an open source email client for Android with multi-folder sync, email signatures, Bcc-to-self, return-address...

Learn more about K-9 Mail

Thunderbird
Do you think this is a good alternative?
Yes
No
Free • Open Source
Email Client
Calendar App
Mac
Windows
Linux
BSD
AppImageHub
Snapcraft
Flathub
PortableApps.com
Haiku
Homebrew
Chocolatey
93 alternatives to Thunderbird
Thunderbird is a free, open source, cross-platform e-mail, news and instant messaging client. The project strategy is modeled after Mozilla Firefox.
Suggest and vote on features
Thunderbird Features
1. Extensible by Plugins/ExtensionsThunderbird can be extended with add-ons, plugins and extensions.
2. Multiple Account supportThunderbird support multiple accounts without the need to logout and login
3. Calendar IntegrationThunderbird lets you sync your tasks and events with your calendar application.
4. Email OrganizerThunderbird allows you to take control of your inbox by filtering and control tools.
5. Dark ModeThunderbird supports dark mode for comfortable usage in low light conditions.
6. Import/Export OPML FeedsImport and export your feed subscriptions into OPML format with Thunderbird.
7. PortableThunderbird can be used from a USB stick or similar with no prior installation.
8. Support for ThemesYou can use themes and templates to change the look and feel of Thunderbird.
9. Integrated Password ManagerThunderbird lets you access all the passwords you’ve saved across your different devices.
IMAP Support
SMTP Support
FOSS
Built-in RSS reader
POP3 Support
Add-ons
Intuitive
Graphical User Interface
Customizable
Built-in Calendar
Thunderbird vs K-9 Mail opinions
Most users think Thunderbird is a great alternative to K-9 Mail.
Microsoft Office Outlook
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Yes
No
Paid • Proprietary
Email Client
Calendar App
Mac
Windows
Online
Android
iPhone
Android Tablet
Windows Phone
iPad
Apple Watch
Android Wear
135 alternatives to Microsoft Office Outlook
Microsoft Outlook, part of the Microsoft 365 (Office) (not to be confused with Microsoft Outlook Express), is a personal information manager that lets you manage your e-mail, calendar, contacts, and tasks.
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Microsoft Office Outlook Features
1. Email OrganizerMicrosoft Office Outlook allows you to take control of your inbox by filtering and control tools.
2. Calendar IntegrationMicrosoft Office Outlook lets you sync your tasks and events with your calendar application.
3. Support for @mentionsMicrosoft Office Outlook supports the use of mentions through @ to a particular user, who will be notified personally.
4. Calendar ViewMicrosoft Office Outlook has a built-in calendar view to have a clear overview of your content over time.
5. Support for AliasesMicrosoft Office Outlook supports aliases, so you can receive email without exposing your main email address
6. Unified inboxView e-mails (or similar) from all accounts in one unified view with Microsoft Office Outlook.
7. Multiple Account supportMicrosoft Office Outlook support multiple accounts without the need to logout and login
8. Works OfflineMicrosoft Office Outlook can be used without the need to connect to the internet.
9. Cloud SyncSync your data (notes, documents, bookmarks, etc.) across your different devices and to the cloud.
Exchange
Native application
Contacts
Built-in Calendar
Onenote Desktop Integration
Address book integration
Dropbox integration
Gmail integration
Office 365 integration
Onedrive integration
Microsoft Office Outlook vs K-9 Mail opinions
This alternative is disputed. Microsoft Office Outlook is still a legitimate alternative to K-9 Mail, but it might have issues that some users think are important.
Guest
Microsoft Office Outlook has more vulnerabilities and so far, seems more of a memory hogger on my device than K-9 Mail. Thank you, K-9 Mail!
Negative comment•
5
Spark Mail
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Yes
No
Freemium • Proprietary
Email Client
Calendar App
Mac
Windows
Android
iPhone
iPad
Apple Watch
58 alternatives to Spark Mail
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.
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Spark Mail Features
1. Multiple Account supportSpark Mail support multiple accounts without the need to logout and login
2. Email SchedulingYou can schedule a marketing, sales, or personal email for a time in the future with Spark Mail.
3. Calendar IntegrationSpark Mail lets you sync your tasks and events with your calendar application.
4. Cloud SyncSync your data (notes, documents, bookmarks, etc.) across your different devices and to the cloud.
5. Email OrganizerSpark Mail allows you to take control of your inbox by filtering and control tools.
6. Dark ModeSpark Mail supports dark mode for comfortable usage in low light conditions.
7. Unified inboxView e-mails (or similar) from all accounts in one unified view with Spark Mail.
8. Works OfflineSpark Mail can be used without the need to connect to the internet.
9. Calendar ViewSpark Mail has a built-in calendar view to have a clear overview of your content over time.
Sorting by folder
Snooze Mail
Ad-free
Sync with Google Calendar
Exchange
Postpone email reception
AI-Powered
Mailspring
Do you think this is a good alternative?
Yes
No
Freemium • Open Source
Email Client
Mac
Windows
Linux
Arch Linux
Fedora
Ubuntu
45 alternatives to 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 version adds read receipts, send later, reminders and more.
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Mailspring Features
1. Unified inboxView e-mails (or similar) from all accounts in one unified view with Mailspring.
2. Multiple Account supportMailspring support multiple accounts without the need to logout and login
3. Dark ModeMailspring supports dark mode for comfortable usage in low light conditions.
4. Support for ThemesYou can use themes and templates to change the look and feel of Mailspring.
5. Ad-freeMailspring doesn't contain any form of external advertising.
6. Email OrganizerMailspring allows you to take control of your inbox by filtering and control tools.
7. Extensible by Plugins/ExtensionsMailspring can be extended with add-ons, plugins and extensions.
Customizable
Email tracking
User friendly
Snooze Mail
Built-in translation
Built-in themes
Auto Update
Notifications
Sidebar
Theme Customization
Delta Chat
Do you think this is a good alternative?
Yes
No
Free • Open Source
Encrypted Chat App
Instant Messenger
Group Chat App
Mac
Windows
Linux
Android
iPhone
Android Tablet
FLATHUB
F-Droid
56 alternatives to Delta Chat
Delta Chat looks and feels like other popular messenger apps, but does not involve centralized control, tracking or selling you, friends, colleagues or family out to large organizations. "Privacy by Design" has never been more fun.
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Delta Chat Features
1. DecentralizedDelta Chat is based on a decentralized infrastructure with no single entity controlling it.
Encrypted Email
IMAP Support
Multiple languages
Electron based
Claws Mail
Do you think this is a good alternative?
Yes
No
Free • Open Source
Email Client
Calendar App
News Reader
Windows
Linux
BSD
88 alternatives to Claws Mail
Claws Mail is an email client (and news reader), based on GTK+, featuring

Quick response Graceful, and sophisticated interface Easy configuration, intuitive operation Abundant features Extensibility Robustness and stability.
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Claws Mail Features
1. LightweightClaws Mail consumes less device resources compared to similar apps.
2. Extensible by Plugins/ExtensionsClaws Mail can be extended with add-ons, plugins and extensions.
3. Multiple Account supportClaws Mail support multiple accounts without the need to logout and login
4. No registration requiredYou can use most of the features in Claws Mail without registration.
5. Import/Export OPML FeedsImport and export your feed subscriptions into OPML format with Claws Mail.
6. Spam FilterClaws Mail can detect unsolicited, unwanted and virus-infected emails, calls, files, etc.
7. PortableClaws Mail can be used from a USB stick or similar with no prior installation.
IMAP Support
Customizable
Multiple languages
Integrated Email Client
Content Filtering
Built-in RSS reader
Betterbird
Do you think this is a good alternative?
Yes
No
Free • Open Source
Email Client
Windows
Linux
Flathub
28 alternatives to Betterbird
Betterbird is a fine-tuned version of Mozilla Thunderbird, Thunderbird on steroids, if you will.
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Betterbird Features
1. Privacy focusedBetterbird is considered a privacy friendly alternative.
2. Multiple Account supportBetterbird support multiple accounts without the need to logout and login
3. Unified inboxView e-mails (or similar) from all accounts in one unified view with Betterbird.
4. Extensible by Plugins/ExtensionsBetterbird can be extended with add-ons, plugins and extensions.
5. PGP EncryptionBetterbird supports PGP, an encryption system used for sending encrypted emails and files.
Add a screenshot
Postbox
Do you think this is a good alternative?
Yes
No
Paid • Proprietary
Email Client
Mac
Windows
70 alternatives to Postbox
Postbox is an email application that helps you organize your work life and get stuff done.
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Postbox Features
1. Multiple Account supportPostbox support multiple accounts without the need to logout and login
2. Extensible by Plugins/ExtensionsPostbox can be extended with add-ons, plugins and extensions.
Exchange
Box.com integration
Tabbed interface
Dropbox integration
IMAP Support
Built-in RSS reader
S/MIME Support
Multiple languages
Onedrive integration
Visual Programming
Canary Mail
Do you think this is a good alternative?
Yes
No
Freemium • Proprietary
Email Client
Calendar App
Mac
Windows
Android
iPhone
Android Tablet
iPad
Apple Watch
61 alternatives to Canary Mail
Email, meet AI. Canary can write your emails, prioritize what needs attention, silence spam & much more. Say hello to your Inbox Copilot!
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Canary Mail Features
1. End-to-End EncryptionCanary Mail has E2E Encryption, for entire or parts of the app.
2. Unified inboxView e-mails (or similar) from all accounts in one unified view with Canary Mail.
3. Multiple Account supportCanary Mail support multiple accounts without the need to logout and login
4. PGP EncryptionCanary Mail supports PGP, an encryption system used for sending encrypted emails and files.
5. No TrackingCanary Mail will not track you or use your personal data.
6. Dark ModeCanary Mail supports dark mode for comfortable usage in low light conditions.
7. Two-factor AuthenticationCanary Mail supports two-factor authentication (2FA).
8. Email OrganizerCanary Mail allows you to take control of your inbox by filtering and control tools.
9. Ad-freeCanary Mail doesn't contain any form of external advertising.
AI-Powered
Email tracking
Snooze Mail
Reminders
Email reminder
Gmail
Email template editor
Read receipts
Spam Filter
Calendar View
BlueMail
Do you think this is a good alternative?
Yes
No
Free Personal • Proprietary
Email Client
Mac
Windows
Linux
Android
iPhone
Chrome OS
Android Tablet
iPad
Apple Watch
27 alternatives to 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.
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BlueMail Features
1. Unified inboxView e-mails (or similar) from all accounts in one unified view with BlueMail.
2. Ad-freeBlueMail doesn't contain any form of external advertising.
3. LightweightBlueMail consumes less device resources compared to similar apps.
4. Multiple Account supportBlueMail support multiple accounts without the need to logout and login
5. Calendar IntegrationBlueMail lets you sync your tasks and events with your calendar application.
IMAP Support
GDPR Compliant
POP3 Support
BlueMail vs K-9 Mail opinions
Some users think BlueMail is a great alternative to K-9 Mail, some don't.