9 Best Email Apps for Windows in 2026: AI, Speed, and Privacy Tested

Microsoft killed Windows Mail in 2024, forcing everyone into the new Outlook app. It's slower, heavier, and locks the best AI features behind a Microsoft 365 subscription. So we set out to find the best email apps for Windows that genuinely replace what Windows Mail did, plus add what was missing.

For the first time in years, there are genuinely good options. AI-powered email clients have matured. Open-source projects have caught up. And a few apps now offer on Windows what used to be Mac-only polish.

We tested 9 email apps on Windows 11 with real inboxes, not empty demo accounts. The average knowledge worker spends 28% of the workweek managing email, so the app you use matters more than you might think. Here's what we found.

Quick Comparison

App	Price	AI Features	Gmail API	Multi-Provider	Best For
FiloMail	Free / $7/mo	Summary, To-dos, Drafts, Search, Chat	✓	Gmail (Outlook in 2.0)	Gmail users who want free AI
Outlook	Free / $7+/mo	Copilot (paid)	✗	✓ All	Microsoft 365 workplaces
Thunderbird	Free	✗	✗	✓ All	Free, open-source, local storage
Mailbird	Free / $49.50 once	ChatGPT	✗	✓ All	Windows-first multi-account
Spark	Free / $8.25/mo	Compose, summaries	Partial	✓ All	Team collaboration
eM Client	Free / $59.95 once	AI compose, translate	✗	✓ All	Calendar + email power user
Superhuman	$25/mo	Summary, drafts, search	✓	Gmail + Outlook	Speed maximalists (web app)
Canary Mail	Free / $3/mo	On-device AI	✗	✓ All	Privacy + encryption
Mailspring	Free / $8/mo	✗	✗	✓ All	Beautiful free alternative

1. FiloMail: Best Free AI Email App for Windows

FiloMail is the only Windows email app that auto-extracts to-do items from your emails and includes AI summaries, smart drafts, and natural language search, all completely free.

Pricing: Free / Plus $7/month (annual) or $10/month
Platforms: Windows, macOS, iOS, Android
Connection: Gmail API via OAuth

FiloMail connects to Gmail through the Gmail API, not IMAP. That means labels sync natively, search operators work, and push notifications arrive instantly instead of on a fetch schedule. On Windows, the app runs the same codebase as the Mac version, so features land on both platforms simultaneously.

The standout feature is to-do extraction. The app reads your emails and pulls out action items automatically. A shipping confirmation becomes "Pick up package Thursday." A client email becomes "Send revised deck by Friday." No other app on this list does this. Your inbox becomes a task list without you doing anything. We covered how this works in our deep dive.

AI Drafts generate replies before you start typing. Open a thread, and a draft is waiting. You can give it instructions: "say yes but push the meeting to next week." Filo AI lets you chat with your inbox. Ask "what did the marketing team say about the Q2 budget?" and get an answer pulled from your emails and attachments. AI Search handles natural language: "invoices from last month" instead of hunting for search operators.

The app is CASA Tier 3 certified by Google, meaning its security practices have been independently verified. FiloMail 2.0 will add Outlook account support and AI agent capabilities, currently in development.

Where it falls short: Gmail only right now. If your primary email is Outlook or Yahoo, FiloMail can't help until 2.0 ships. No offline mode. The Windows app is Electron-based, not a native Win32 application, though performance is solid on modern hardware.

Bottom line: If you use Gmail on Windows and want AI that's actually useful, not a checkbox feature. FiloMail is the best free option by a wide margin. The to-do extraction alone makes it worth installing.

Try FiloMail free → filomail.com

2. Microsoft Outlook: Best for Microsoft 365 Workplaces

The new Outlook app is now the default Windows email client. It's the best choice if your company runs Microsoft 365, but a downgrade for everyone else.

Pricing: Free / Microsoft 365 from $6.99/mo
Platforms: Windows, macOS, iOS, Android, Web
Connection: Microsoft Graph (native), IMAP (Gmail/others)

The new Outlook replaced both Windows Mail and the classic Outlook desktop app. It's essentially Outlook web in a wrapper, which means it's faster to update but lost some power-user features from the classic version.

If your workplace runs on Microsoft 365, Outlook is non-negotiable. Teams, SharePoint, OneDrive, and Calendar all work natively. Copilot AI integration adds thread summaries, draft assistance, and meeting prep, but only with a Microsoft 365 subscription.

Focused Inbox learns which emails matter to you and sorts them automatically. The calendar integration is the best of any app on this list for scheduling.

Where it falls short: Gmail accounts connect over IMAP, which means you lose labels, categories, and advanced search operators. That's a real downgrade if Gmail is your primary account. Copilot requires a paid subscription. The new Outlook is noticeably slower to launch than lighter alternatives. And many power users miss features from classic Outlook that haven't been carried over.

Bottom line: If your company uses Microsoft 365, install it. If you use Gmail as your primary email on Windows, Outlook gives you a degraded version of your own inbox. You're better off with a client that speaks Gmail natively.

3. Thunderbird: Best Free Open-Source Email

Thunderbird is the best free email client for Windows: fully open-source, supports every email provider, and stores everything locally so your email never sits on a third-party server.

Pricing: Free (donation-supported)
Platforms: Windows, macOS, Linux
Connection: IMAP / POP3 / Exchange (via add-on)

Thunderbird has been around for two decades, and Mozilla's recent investment shows. The Supernova redesign in 2023-2024 modernized the interface without sacrificing the flexibility that power users depend on.

Mail filters and rules are more powerful than any other free client. You can create multi-condition rules that automatically sort, tag, move, or reply to emails. Add-ons extend functionality further: calendar, tasks, and even Exchange support through third-party plugins. Everything stores locally, which means your email data never touches a company's cloud servers.

Where it falls short: No AI features. The learning curve is steep, and the settings menu alone has dozens of panels. No mobile app (desktop only). The IMAP connection means Gmail labels sync as folders, and you lose Gmail-specific search operators. The UI, while improved, still feels denser than modern alternatives.

Bottom line: If you want a powerful, free, privacy-respecting email client and don't need AI or mobile sync, Thunderbird is the gold standard on Windows. It's what you install when you trust no one else with your email.

4. Mailbird: Best Windows-Native Experience

Mailbird is the most Windows-native email app on this list. It's built specifically for Windows with fast keyboard shortcuts, a clean interface, and integrations with tools like Slack and WhatsApp built directly into the sidebar.

Pricing: Free trial / Standard $49.50 / Premium $99.75 (one-time, plus yearly update fee)
Platforms: Windows, Mac
Connection: IMAP / POP3 / Exchange

Mailbird has been a Windows-first email client for years, and it shows. The interface is clean and responsive. Keyboard shortcuts are customizable. The unified inbox handles unlimited email accounts across providers: Gmail, Outlook, Yahoo, iCloud, all in one view.

The sidebar integrates directly with third-party apps: Google Calendar, Slack, WhatsApp, Todoist, and Dropbox without switching windows. ChatGPT integration provides AI-powered composition assistance. Snooze, sender blocking, and mail filters handle inbox management.

Where it falls short: IMAP-only for Gmail, so labels become folders and search is limited. The one-time pricing sounds good until you add the yearly update fee ($10-20/year). AI features are basic: ChatGPT integration but no inbox-native AI like to-do extraction or natural language search. No Linux support.

Bottom line: If you want an email app that feels like it was built for Windows, not ported from Mac or wrapped from the web. Mailbird is the closest you'll get.

5. Spark: Best for Team Email

Spark is the best Windows email app for teams. It's the only desktop client with shared inboxes, email delegation, internal comments, and collaborative drafts that work across all platforms.

Pricing: Free / Plus $8.25/month / Pro $16.58/month (billed annually)
Platforms: Windows, macOS, iOS, Android
Connection: IMAP with partial Gmail API

Spark's Smart Inbox automatically groups emails into Personal, Notifications, and Newsletters. The AI compose assistant generates replies from brief prompts and adjusts tone on demand. The built-in calendar syncs with Google Calendar and Outlook Calendar.

Where Spark stands apart is collaboration. Assign emails to teammates, leave internal comments that clients never see, collaborate on drafts before sending. On Windows, all of this works the same as on Mac or mobile.

Where it falls short: Spark stores emails on their servers to enable collaboration, so privacy-conscious users should note this. IMAP connection means Gmail labels sync with a delay. AI features are less developed than FiloMail's or Superhuman's.

Bottom line: If your team shares email responsibilities, Spark is the right tool. Solo users looking for AI or deep Gmail integration have better options above.

6. eM Client: Best for Calendar + Email Power Users

eM Client is the best all-in-one desktop app for Windows if you need email, calendar, contacts, and tasks in a single native client, with PGP encryption and AI compose built in.

Pricing: Free (2 accounts) / Pro $59.95 (one-time)
Platforms: Windows, macOS
Connection: IMAP / Exchange / Google / iCloud

eM Client supports every major email service natively: Gmail, Exchange, iCloud, Outlook.com. The calendar integration is deep: drag emails to create calendar events, inline RSVP, and a side-by-side mail+calendar view that Outlook users will recognize.

AI compose tools and automatic translation are built in. PGP and S/MIME encryption are native, not add-ons. The interface is polished and customizable, so you can adjust layouts, themes, and density to match how you work.

Where it falls short: The free tier limits you to 2 email accounts. Gmail connects over IMAP, not Gmail API, so labels and search operators are limited. The app can feel heavy on older hardware. No mobile version (desktop only).

Bottom line: If you live in calendar and email equally and want one app for both on Windows, eM Client is the strongest option. The one-time pricing is refreshing in a world of subscriptions.

7. Superhuman: Fastest Email on Windows (Web App)

Superhuman is the fastest email experience available on Windows, but it runs as a web app in your browser, not as a native desktop client, and costs $25/month with no free tier.

Pricing: $25/month (billed annually, no free tier)
Platforms: Web (works on Windows via browser), macOS, iOS, Android
Connection: Gmail API / Outlook API

Superhuman's speed is real. Every action (archive, snooze, reply) is designed to be instantaneous. Split Inbox sorts email into custom categories. AI drafts generate replies in your voice. Conversational search understands natural language.

On Windows, Superhuman runs in Chrome or Edge as a web app. You can pin it to the taskbar and it works like a desktop app, but it's not native. No system tray, no offline access, no Windows notifications integration beyond what the browser provides.

Where it falls short: $25/month ($300/year) with no free tier. On Windows specifically, the web-app nature means no offline, no native notifications, and no system-level integrations. If you're paying $300/year for email, you might expect a native Windows app. Also check our Superhuman alternatives guide, where several apps offer similar features for less.

Bottom line: If speed is everything and budget isn't a concern, Superhuman delivers. But on Windows specifically, the lack of a native app makes it harder to justify versus apps that actually integrate with the OS.

8. Canary Mail: Best for Privacy on Windows

Canary Mail is the best privacy-focused email app for Windows, with built-in PGP encryption, tracking pixel blocking, and AI that processes entirely on your device.

Pricing: Free / Growth $3/month / Pro+ $8.33/month
Platforms: Windows, macOS, iOS, Android
Connection: IMAP

Canary leads with privacy. PGP encryption is built in, not bolted on through a plugin. SecureSend lets you send encrypted emails to anyone, and recipients open them through a secure link. On-device AI means summaries and categorization happen locally without your email data leaving your machine.

The privacy dashboard shows which senders track you with pixels. Read receipt blocking is automatic. Multi-provider support works across Gmail, Outlook, Yahoo, and iCloud.

Where it falls short: IMAP means Gmail labels become folders and advanced search is limited. The free tier is constrained. AI capabilities are less developed than dedicated AI email clients. The app can feel slower than lighter alternatives.

Bottom line: If privacy and encryption matter more than AI power, Canary Mail covers ground that most Windows email apps ignore entirely.

9. Mailspring: Best Beautiful Free Alternative

Mailspring is the best-looking free email client for Windows. It's open-source, uses a native C++ sync engine for fast performance, and offers a polished experience that rivals paid alternatives.

Pricing: Free / Pro $8/month
Platforms: Windows, macOS, Linux
Connection: IMAP

Mailspring stands out on looks. The interface is modern and clean, closer to Superhuman's aesthetic than Thunderbird's density. The native C++ sync engine uses about 50% less RAM than Electron-based clients and launches in under a second.

Unified inbox, snooze, send later, and mail rules are all included in the free tier. Active development resumed in 2025, with fixes for long-standing issues and a rebuilt calendar. Pro adds read receipts, link tracking, and contact profiles.

Where it falls short: No AI features. Gmail connects via IMAP, so labels and search operators are limited. The Pro tier at $8/month is pricey for what it adds. The app lacks deep integrations that Mailbird or eM Client offer.

Bottom line: If you want a free email app that looks good and runs fast on Windows, Mailspring punches above its weight. It's what Thunderbird would be if Mozilla hired a designer.

Gmail API vs IMAP: Why It Matters on Windows

Most email apps on Windows connect to Gmail through IMAP, an old protocol that treats Gmail like any generic email account. That means your labels become folders, search operators don't work, and notifications depend on how often the app polls the server.

A few apps use the Gmail API instead: Google's official interface for third-party clients. The difference is significant:

Feature	Gmail API	IMAP
Labels	✓ Native sync	✗ Converted to folders
Search operators	✓ Full support	✗ Limited
Push notifications	✓ Instant	⚠ Fetch interval
Categories	✓ Supported	✗ Not available
Security	✓ OAuth only	⚠ Varies

On this list: FiloMail and Superhuman use Gmail API. Everyone else uses IMAP. If Gmail is your primary account on Windows, this matters. We covered this in detail in our Gmail clients comparison.

What Happened to Windows Mail?

In 2024, Microsoft deprecated the built-in Windows Mail app and replaced it with the new Outlook for Windows. The transition was not optional. Windows Mail users were migrated automatically.

The new Outlook is essentially a web app wrapper around Outlook.com. It's more capable than Windows Mail was, but also heavier, slower to launch, and packs its best features (Copilot AI, advanced rules) behind Microsoft 365 subscriptions. For users who liked Windows Mail's simplicity, the forced migration felt like a downgrade.

If you're one of those users, the apps on this list are your real alternatives.

How We Tested

We used each app on Windows 11 with a real Gmail inbox containing 15,000+ emails. Here's what we evaluated:

Launch speed and memory: How quickly the app starts and how much RAM it consumes in steady state.
Notification reliability: Push vs. fetch. Do new emails appear within seconds or minutes?
AI usefulness: Does the AI save time or just add buttons? Tested with real email workflows.
Multi-account switching: How smooth is switching between Gmail, Outlook, and other accounts?
Keyboard shortcuts: How much can you do without touching the mouse?
Offline capability: Can you read and compose emails without an internet connection?
Windows integration: Taskbar behavior, system tray, Start Menu search, Focus Assist compatibility.

How to Choose the Right Windows Email App

Start with what matters most:

"I use Gmail and want AI that actually helps" → FiloMail. Free AI, to-do extraction, Gmail API.
"My company uses Microsoft 365" → Outlook. Non-negotiable for corporate.
"I want free, private, and open-source" → Thunderbird. Local storage, no cloud.
"I want the most Windows-native experience" → Mailbird. Built for Windows first.
"My team shares email" → Spark. Collaboration on desktop.
"I need calendar + email in one app" → eM Client. Best all-in-one.
"I want the fastest email possible" → Superhuman. $25/mo, web-only on Windows.
"Privacy and encryption come first" → Canary Mail. PGP + on-device AI.
"I want free and beautiful" → Mailspring. Open-source, fast, clean.

For deeper comparisons, check our best AI email apps guide, Gmail clients comparison, and Superhuman alternatives.

Frequently Asked Questions

What is the best free email app for Windows?

Thunderbird is the most powerful free option: fully open-source, supports every provider, and stores email locally. FiloMail is the best free option if you use Gmail and want AI features like auto-summaries, to-do extraction, and smart drafts at no cost. Mailspring is a solid free alternative if you want something modern-looking.

What replaced Windows Mail?

Microsoft replaced Windows Mail with the new Outlook for Windows in 2024. The transition was automatic, and existing Windows Mail users were migrated to the new Outlook app. It's more capable but also heavier and locks AI features behind Microsoft 365 subscriptions.

Is the new Outlook app good?

For Microsoft 365 users, yes. Teams, SharePoint, and Calendar all integrate natively without setup. For everyone else, it's mixed. It's slower than Windows Mail was, the interface is busier, and the best AI features (Copilot) require a paid subscription. If you use Gmail as your primary email, the IMAP connection gives you a degraded Gmail experience.

Does it matter if an email app uses Gmail API or IMAP on Windows?

Yes. Gmail API apps (FiloMail, Superhuman) sync labels natively, support full search operators, and deliver instant push notifications. IMAP apps (Thunderbird, Mailbird, eM Client, Spark) treat Gmail like a generic mailbox: labels become folders, and search is limited. If Gmail is your primary account, this is a real decision factor. See our Gmail clients guide for details.

Can I use multiple email accounts in one Windows email app?

Yes. Most apps on this list support unlimited accounts. Mailbird, Thunderbird, Spark, eM Client, and Canary Mail all handle Gmail, Outlook, Yahoo, and iCloud in one unified inbox. FiloMail supports multiple Gmail accounts. eM Client's free tier limits you to 2 accounts.

Which Windows email apps have AI features?

FiloMail has the most comprehensive free AI: summaries, to-do extraction, smart drafts, natural language search, and inbox chat. Spark offers AI compose and summaries. eM Client has AI compose and auto-translation. Mailbird integrates ChatGPT. Superhuman has AI drafts and search. Microsoft Outlook has Copilot (paid). Thunderbird, Mailspring, and Canary Mail have no or minimal AI.

Is Thunderbird still good in 2026?

Yes. The Supernova redesign modernized the interface, and Mozilla continues active development. Thunderbird remains the most powerful free email client available on Windows. It just doesn't have AI features. If you want flexibility, privacy, and don't mind a learning curve, it's excellent.

Can I use Superhuman on Windows?

Yes, but only as a web app in your browser. Superhuman doesn't have a native Windows desktop application. You access it through Chrome or Edge and can pin it to your taskbar. This means no offline access, no system tray icon, and limited Windows notification integration.

Which Windows email apps work offline?

Thunderbird offers the best offline experience with full local storage. Mailbird, eM Client, and Canary Mail also support offline reading and composing. Spark has partial offline support. FiloMail, Superhuman, and Mailspring require an internet connection for most features.

What is the most secure email app for Windows?

For encryption: Canary Mail has built-in PGP and on-device AI processing. eM Client supports PGP and S/MIME. Thunderbird supports OpenPGP natively. For data protection: FiloMail is CASA Tier 3 certified by Google. For privacy: Thunderbird stores everything locally, so your email never touches a third-party server.

9 Best Email Apps for Windows in 2026 (We Tested Them All)