Mailbird alternatives: 5 apps ranked by verified data

Facts checked Oct 25, 2026AppBreakup editorialHow we rank

Common reasons people leave Mailbird: no mobile apps, and free tier only covers one account. We ranked 5 alternatives by how directly each one replaces Mailbird, then by reviews, real visits and how recently each app's facts were checked against its own website. eM Client currently ranks first.

Quick comparison

#	App	Pricing	Open source	Platforms	Verified facts	Score
1	Thunderbird	Open source	Yes	Windows, macOS, Linux +1	5 of 5	62.6

1. ThunderbirdTop pick
Best for: Desktop users who want a free, private, customisable mail and calendar app
Open sourceWindows, macOS, Linux, Android
62.6
score / 100
Why switch from Mailbird
Free and open source with unlimited accounts and add-ons.
Pros
Free, open source and funded by donations, with no ads
Built-in OpenPGP, calendar, filters and many add-ons
Runs on Windows, Mac, Linux and Android
Cons
No web version and no released iOS app yet
Add-ons sometimes break after major updates
Exchange setups can need extra configuration
Visit Thunderbird Details and reviews
How this score is calculated
Editorial fit ×0.387
Reviews ×0.363
Clicks (90 days) ×0.150
Freshness ×0.1585
Votes ×0.150
0 counted reviews, 0 up and 0 down votes. Full formula
Is Thunderbird a good Mailbird alternative?
Verified facts
5 of 5 verified
Desktop platforms
Windows, Linux, macOS
Checked Oct 25, 2026thunderbird.net(opens source in a new tab)
Price
Free, funded by donations
Checked Oct 25, 2026thunderbird.net(opens source in a new tab)
Mobile app
Open-source Android app
Checked Oct 25, 2026thunderbird.net(opens source in a new tab)
Android app origin
Formerly K-9 Mail
Checked Oct 25, 2026github.com(opens source in a new tab)
Android app license
Apache-2.0
Checked Oct 25, 2026github.com(opens source in a new tab)

The best Mailbird alternative for…

The highest-ranked app in this list for each need.

Best Mailbird alternative for most people

eM Client

A deeper desktop client with calendar, tasks and PGP on Windows and Mac.

Best Mailbird alternative for a free option

Thunderbird

Free and open source with unlimited accounts and add-ons.

Best Mailbird alternative for a free plan you can upgrade

Spark

Free for unlimited accounts, with mobile apps as well as desktop.

Best Mailbird alternative for open source

Mailspring

Open-source client with a free tier and Linux support.

Best Mailbird alternative for Mac

Microsoft Outlook

The new Outlook for Windows is free and handles Gmail and IMAP accounts too.

Best Mailbird alternative for Windows

eM Client

A deeper desktop client with calendar, tasks and PGP on Windows and Mac.

Best Mailbird alternative for Linux

Thunderbird

Free and open source with unlimited accounts and add-ons.

Best Mailbird alternative for iPhone and Android

Spark

Free for unlimited accounts, with mobile apps as well as desktop.

Best Mailbird alternative for working in the browser

Microsoft Outlook

The new Outlook for Windows is free and handles Gmail and IMAP accounts too.

Mailbird alternatives: common questions

What is the best alternative to Mailbird?

eM Client ranks first right now. A deeper desktop client with calendar, tasks and PGP on Windows and Mac. Thunderbird and Spark follow it in our ranking.

Is there a free alternative to Mailbird?

Yes. eM Client (free plan + paid), Thunderbird (open source), Spark (free plan + paid) and Mailspring (free plan + paid) have a free option. Check each app's verified facts for current plan limits.

Is there an open-source alternative to Mailbird?

Yes: Thunderbird and Mailspring.

Which Mailbird alternatives work on Linux?

Thunderbird and Mailspring run on Linux.

Why do people switch from Mailbird?

The complaints we hear most: no mobile apps; free tier only covers one account; integrations are mostly embedded web apps.

How is this list ranked?

Every app is scored with the same published formula: how directly it replaces Mailbird, reviews (weighted by verification), visits from AppBreakup, how recently its facts were checked against its own website, and reader votes.