Outlook alternatives 2026: what to use instead of New Outlo…

New Outlook doesn’t just show you email — it relays your third-party IMAP credentials through Microsoft’s cloud servers before they reach your inbox. Heise Online documented this in November 2023; Germany’s Federal Data Protection Commissioner subsequently announced intent to investigate through EU data protection authorities. If you use Gmail, Fastmail, or any non-Microsoft IMAP account alongside Outlook, that architecture means Microsoft’s infrastructure holds your IMAP password indefinitely. Here are the six alternatives that use the standard local-connection model instead.

Try Mailbird — best Windows alternative

Why People Want to Leave New Outlook

New Outlook routes third-party IMAP credentials through Microsoft’s cloud — documented by Heise Online in November 2023, confirmed by Microsoft as the intended architecture. For users connecting Gmail, Fastmail, or self-hosted IMAP, this means Microsoft holds your credentials and email content on Azure servers as long as you use the client.

The reason this page exists is not aesthetics or feature gaps. It’s a documented privacy issue that Microsoft has confirmed.

In November 2023, German tech magazine Heise Online reported that when you add a third-party IMAP account (Gmail, Fastmail, a private server) to New Outlook for Windows, the app transmits your IMAP login credentials to Microsoft’s Azure infrastructure — not to your mail provider. (Source: Heise Online, Nov 2023.)

This is not a bug. It’s New Outlook’s deliberate sync architecture. The client doesn’t communicate directly with your mail server the way classic Outlook, Thunderbird, or Mailbird do. Instead, Microsoft’s cloud acts as a proxy: it receives your credentials, connects to your mail server on your behalf, and caches your email on Azure. Microsoft’s own statement confirmed credentials are retained “as long as you actively use the client.” (Source: Born’s Tech and Windows World, Nov 2023.)

Germany’s Federal Data Protection Commissioner announced intent to investigate the matter through EU data protection authorities. The Hacker News thread at the time noted that Microsoft had given inconsistent answers to c’t magazine about this behaviour. (Source: Hacker News, Nov 2023.)

That’s why people are looking for alternatives.

Mailbird — best Outlook alternative for Windows

Mailbird connects to your mail server directly — no cloud proxy, no Microsoft infrastructure in the path. It’s the most polished Windows-native alternative with a genuine unified inbox and integrations dock (Slack, WhatsApp, Google Calendar).

Mailbird is the straightforward Windows replacement.

How it handles credentials. Mailbird connects to your mail server directly. Your Gmail OAuth token or IMAP password goes from your machine to Google’s (or your provider’s) servers. Mailbird’s own servers are not in the path. This is the standard architecture that classic Outlook, Thunderbird, and most desktop clients use.

What makes it worth paying for. The unified inbox works across Gmail, Outlook, IMAP, and Exchange accounts in a single view. The app panel lets you dock Google Calendar, WhatsApp, Slack, or Todoist without leaving the email window — a feature density we haven’t matched in any competing client.

Pricing (verified April 2026, getmailbird.com/pricing):

Free: 1 account, limited features
Premium subscription: €2.30/month billed yearly
One-time license: €73.80 (lifetime use, optional upgrade insurance extra)

The one-time license is the better long-term value if you plan to use the client for more than three years.

Caveats. Windows-first. The Mac build launched on the Apple App Store in September 2025, but the Windows experience has historically been the more complete product. No Linux build.

Try Mailbird — 14-day money-back guarantee

Spark — best for Mac and iOS-first users

Spark from Readdle is the most polished collaborative email client on Mac. Smart Inbox, AI reply drafts, and team features are strong. The privacy caveat: Spark routes some features through Readdle’s servers, which is a different architecture from fully local clients.

Spark’s Smart Inbox groups newsletters, notifications, and personal emails automatically. The AI-assisted reply drafting and thread summarisation are genuinely useful rather than novelty features. The Windows version (available on the Microsoft Store) was released in 2022 and has matured — it’s a credible cross-platform choice if you value Mac-first design sensibility.

Pricing (from sparkmailapp.com/pricing): Free plan is useful for individuals. Premium Individual is $4.99/month ($59.99/year). Team plans add shared inboxes and collaboration drafts.

Privacy caveat. Spark’s servers handle some features (push notifications, Smart Inbox categorisation). The privacy model is different from Mailbird or Thunderbird’s fully local approach. Readdle has a published privacy policy, but the architecture is not fully client-side. For users switching from New Outlook specifically on privacy grounds, it’s worth reading Readdle’s privacy terms before committing.

Thunderbird — best cross-platform, free option

Thunderbird is fully free, open-source (MPL 2.0), and the only client on this list that runs on Windows, Mac, and Linux. It added native Exchange support in Release 145 (November 2025), which means it’s now a credible alternative for users with one Exchange account alongside Gmail.

For anyone who wants zero cost, open-source verifiability, and no cloud sync of any kind, Thunderbird is the answer.

The 2023 “Supernova” redesign (version 115) addressed Thunderbird’s most persistent criticism — the dated UI. The unified toolbar, vertical three-pane layout, and card view brought it closer to the experience of modern webmail clients without sacrificing configurability. (Source: Thunderbird blog, July 2023.)

Thunderbird runs on Windows, Mac, and Linux. Credentials go from your machine to your mail provider. The MZLA Foundation publishes the full source code.

Weaknesses. No integrated app panel. Calendar works via the built-in extension but isn’t as smooth as Mailbird’s or Outlook’s. Gmail OAuth setup has historically been more steps than it should be.

Price. Free. Accepts optional donations at thunderbird.net.

On Windows and need Slack + WhatsApp alongside email? Try Mailbird. On Linux or need open-source verification? Use Thunderbird — it’s free at thunderbird.net.

eM Client — best if you split time between Windows and Mac

eM Client runs on Windows and macOS with genuine feature parity. It handles Exchange, Gmail, iCloud, and IMAP accounts, and includes a built-in calendar and contact manager. Since the October 2024 Postbox acquisition, it’s the natural upgrade path for former Postbox users.

eM Client runs on Windows and macOS with genuine feature parity — a rarity in this category. It handles Exchange, Gmail, iCloud, and IMAP accounts.

The free tier allows up to two accounts and is genuinely usable for a single-mailbox setup.

Pricing (verified April 2026, emclient.com/pricing):

Free: 2 accounts, personal use
Personal: €39.95/year or €59.95 one-time (up to 3 devices)
Business: €49.95/year per device

Note: eM Client acquired Postbox in October 2024 and ended Postbox development. Former Postbox users are the natural migration target. (Source: eM Client blog.)

Mimestream — best for Gmail-only users on Mac

Mimestream uses the Gmail API natively (not IMAP), which means labels, stars, and categories work exactly as they do in the Gmail web interface. Mac-only and Gmail-only — but for that specific combination, it’s exceptional.

Mimestream is worth a mention even though it’s Mac-only and Gmail-only, because for that specific use case it’s exceptional. It uses the Gmail API natively, which means labels, stars, and categories work exactly as they do in the Gmail web interface.

Pricing: $4.99/month or $49.99/year after a 14-day trial. Mac only.

If you’re on Windows or use non-Gmail accounts, this is not your client. If you’re a Mac + Gmail user who wants a native app experience, it’s worth the trial.

Apple Mail — for macOS / iOS ecosystem users

Apple Mail ships with every Mac and iPhone, handles Exchange, Gmail, iCloud, and IMAP, and doesn’t route email through third-party servers. Since macOS Sequoia 15.4 (March 2025), it gained Apple Intelligence-powered inbox categories — bringing it closer to Gmail’s sorting capabilities.

Apple Mail is the zero-cost, pre-installed option on macOS and iOS. Privacy-wise, connections go from your device to your mail provider — Apple doesn’t proxy IMAP connections.

macOS Sequoia 15.4 update (March 2025). The Sequoia 15.4 update brought Apple Intelligence-powered inbox categories (Primary, Transactions, Updates, Promotions), Priority Messages surfaced at the top, and AI-generated email summaries — matching what Gmail’s web interface has offered for years, but processing locally on-device.

Weakness. Features are intentionally minimal. No unified inbox view that matches Mailbird’s, no docked apps panel, no snooze or advanced keyboard shortcuts for triage. If you manage multiple accounts actively, you’ll outgrow it quickly.

Which One Based on Your Setup

The right Outlook alternative depends on platform, budget, and whether you need team features, open-source verification, or Gmail-native performance.

Your situation	Best pick
Windows, multiple accounts, want the best native experience	Mailbird
Windows, zero budget, privacy-first	Thunderbird
Mac primary, multiple providers	Spark
Mac + Gmail only	Mimestream
Windows + Mac household	eM Client
Apple ecosystem, basic needs	Apple Mail
Microsoft 365 organization, Exchange-only	New Outlook (acceptable in this context)

The common thread in every non-Microsoft option: credentials go from your machine directly to your mail provider. That’s the architecture that was standard before New Outlook changed it.

When Classic Outlook Is Still the Right Answer

Classic Outlook remains the right answer for Microsoft 365 organizations where every mailbox is on Exchange Online. The privacy concern with New Outlook doesn’t apply when your data is already in Microsoft’s cloud by design.

There are situations where staying with Outlook is the correct decision:

Microsoft 365 organizations. If every mailbox is @yourdomain.com on Exchange Online — and your organization already operates within Microsoft’s cloud infrastructure — New Outlook’s sync-through-cloud architecture is a non-issue. Microsoft already holds the data. The Teams, SharePoint, and Copilot integration that Outlook provides natively is hard to replace.

Classic Outlook (not New Outlook). Classic Outlook stores email locally in PST/OST files and connects directly to your mail server. The privacy concern documented by Heise Online applies to New Outlook, not classic Outlook. If you’re on classic Outlook via a Microsoft 365 subscription and connected to Exchange, there’s no compelling privacy reason to switch.

Multiple platforms with consistent experience needed. If you use Outlook on Windows, Mac, iOS, and Android and want a consistent experience across all four, no single alternative matches that coverage. Mailbird covers Windows + Mac; Thunderbird covers Windows + Mac + Linux; neither has a strong iOS companion.

Frequently asked questions

Does Mailbird work as a direct Outlook replacement? — yes for personal use

For personal use with multiple email accounts from different providers, yes — Mailbird replaces New Outlook’s functions without routing your credentials through a third-party cloud. For Exchange/Teams/SharePoint integration in a Microsoft 365 organization, no third-party client replicates Outlook’s native depth.

Is classic Outlook safer than New Outlook? — yes for non-Microsoft accounts

Classic Outlook connects directly to your mail server via IMAP/Exchange protocols. The credential-routing issue documented by Heise Online applies specifically to New Outlook. If you have access to classic Outlook via a Microsoft 365 subscription, using it for non-Microsoft accounts avoids the architecture concern.

Can I keep my Outlook email address and use a different client? — yes

Yes. Your @outlook.com or @hotmail.com email address is tied to your Microsoft account, not to the Outlook client. Any IMAP-compatible client — Mailbird, Thunderbird, eM Client — can connect to it using IMAP/SMTP or OAuth. You keep the address; you just use a different app to access it.

Does Thunderbird support Exchange accounts? — yes, since November 2025

Yes, as of Release 145 (November 2025), Thunderbird added native Exchange support via EWS. Earlier versions required IMAP or a third-party add-on.

What is the best free Outlook alternative? — Thunderbird

Thunderbird. It’s fully free, open-source, supports multiple accounts, and its 2023 Supernova redesign significantly improved the UI. For zero cost, it’s the strongest alternative to any commercial email client.

Is Apple Mail a good Outlook alternative on Mac? — yes for basic needs

For basic email management on macOS, yes — Apple Mail handles Exchange, Gmail, iCloud, and IMAP, doesn’t route connections through third-party servers, and since Sequoia 15.4 (March 2025) has Apple Intelligence inbox categories. For power users who manage multiple accounts with heavy keyboard use, Mailbird or Spark are stronger.

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