email client · MZLA Technologies / Mozilla

Mozilla Thunderbird

Free, open-source email client for Windows, macOS, Linux and Android, with calendar, OpenPGP and S/MIME built in.

88/100

#1 of 10 email clients
Facts checked 8 Oct 2026

In short

Thunderbird is free and funded by donations¹.
Desktop apps run on Windows, macOS and Linux; a mobile app runs on Android².
Native Exchange access arrived in version 145 (November 2025) over EWS; version 154 added Microsoft Graph, both for email only^6,9.
OpenPGP, CalDAV and CardDAV appear in the 157.0 release notes, dated 30 September 2026; S/MIME appears in the 140.0 ESR notes^3,4.
Mozilla says email is stored on your device and is not sent to Mozilla or Thunderbird servers⁷.

Thunderbird suits people who want a free client with a unified inbox, calendar and built-in OpenPGP and S/MIME^1,3,4. Mail stays on your device, per its privacy policy⁷. The catch: Exchange access covers email only^6,9, and the vendor pages do not list snooze or undo send^1,3,5.

Best for: People who want a free, open-source client with built-in encryption.

Where the points come from

Mail and accounts23 of 27

Calendar and contacts9 of 9

Privacy and encryption24 of 28

Systems and upkeep11 of 15

Price21 of 21

Mail and accounts 23 of 27 points

Rule	What is published	Points
Account types	IMAP, POP3, Exchange, Gmail and Microsoft 365 sign-inRelease notes cover IMAP/POP setup and Gmail OAuth2; Exchange posts cover EWS, Graph and Microsoft OAuth2 sign-in^3,6,9.	12 / 12
Unified inbox	Yes'Manage all accounts separately or in a unified inbox'¹.	4 / 4
Mail tools	Scheduled send, TemplatesRelease notes refer to a 'Send Later' feature and to message templates. Snooze and undo send are not listed on pages read^5,10.	4 / 8
Filters and rules	YesRelease notes describe message filters and the Quick Filter⁴.	3 / 3

Calendar and contacts 9 of 9 points

Rule	What is published	Points
Built-in calendar	YesHome page promises calendars in one app; release notes cover calendar setup and event fixes^1,4.	6 / 6
CalDAV and CardDAV	YesRelease notes mention CalDAV calendars and CardDAV address books syncing^3,4.	3 / 3

Privacy and encryption 24 of 28 points

Rule	What is published	Points
OpenPGP	YesRelease notes cover OpenPGP key import, discovery and encryption, built into the app^3,4.	7 / 7
S/MIME	YesRelease notes mention S/MIME signed-mail display and ECDH encryption and decryption; counted as built-in^4,5.	6 / 6
Blocks tracking pixels	Not publishedNot published on the vendor's pages^1,3.	0 / 4
Open-source apps	YesHome page says Thunderbird is open source; the Android app is Apache-2.0 on GitHub^1,8.	6 / 6
Mail stays on your device	YesPolicy: messages are stored and processed locally; sync runs directly between Thunderbird and your provider⁷.	5 / 5

Systems and upkeep 11 of 15 points

Rule	What is published	Points
Other systems	macOS, Linux, AndroidDownload page lists desktop builds for macOS and Linux, and Android through Google Play and F-Droid².	6 / 10
Released in the last year	YesThunderbird 157.0 was released on September 30, 2026³.	5 / 5

Price 21 of 21 points

Rule	What is published	Points
No ads in the app	YesOpen-source app; the home page says it does not 'sell ads in your inbox'¹.	3 / 3
Free plan	Yes'Free forever'; the full app is free¹.	6 / 6
Cost of a year	$0The full app is free, funded by optional donations¹.	12 / 12

The rule behind each line: how we score email clients.

Plans and prices

As the vendor lists them, before tax. Prices are in US dollars unless the plan shows euros; the points use US dollars, with euros converted at the ECB rate.

Plan	Price as listed	Per month	Notes
Thunderbird1 person	Free¹	$0	Funded by optional donations; no paid plan

Strengths

Free with no ads in the inbox, funded by donations¹.
Mail is stored and processed on your device, not sent to Mozilla⁷.
Includes a unified inbox across accounts¹.
Release notes show OpenPGP, S/MIME, CalDAV and CardDAV support^3,4.

Limits

Native Exchange access handles email only; calendar and address book are not yet available^6,9.
No iOS app is listed on the download pages².
Microsoft plans to switch off EWS on Microsoft 365 in phases from October 2026; Graph support is in the Release channel, not ESR 153⁹.
Snooze and undo send are not listed on the vendor pages^1,3,5.

What MZLA Technologies / Mozilla says

Vendor claims. We show them, but they earn no points.

Thunderbird says it does not collect personal data or secretly train AI with private conversations¹.

Other email clients

2
BetterbirdThunderbird users who want more control over how mail is listed, sorted and searched
78/100
$0cost of a year
3
BlueMailPeople who want a free app with PGP, a calendar and many accounts
78/100
$0cost of a year
4
eM ClientPeople who want PGP, S/MIME and a calendar in one paid Windows app
73/100
$55.87/yrcost of a year
5
Microsoft OutlookPeople who want a free app with a calendar, scheduled send and undo send
67/100
$0cost of a year

Mozilla Thunderbird vs Betterbird · Mozilla Thunderbird vs BlueMail · All 10 email clients

Sources

Thunderbird: Make Email Yours, Thunderbird. Accessed 8 Oct 2026.
Download Thunderbird: all platforms and languages, Thunderbird. Accessed 8 Oct 2026.
Thunderbird 157.0 release notes, Thunderbird. Accessed 8 Oct 2026.
Thunderbird 140.0esr release notes, Thunderbird. Accessed 8 Oct 2026.
Thunderbird 128.0esr release notes, Thunderbird. Accessed 8 Oct 2026.
Thunderbird adds native Microsoft Exchange email support, Thunderbird Blog. Accessed 8 Oct 2026.
Thunderbird privacy policy, Thunderbird. Accessed 8 Oct 2026.
thunderbird/thunderbird-android, GitHub. Accessed 8 Oct 2026.
Thunderbird Desktop New Protocol Support: Microsoft Graph API, Thunderbird Blog. Accessed 8 Oct 2026.
Thunderbird 115.0esr release notes, Mozilla Thunderbird. Accessed 8 Oct 2026.

Website: www.thunderbird.net · Markdown version · We are not affiliated with MZLA Technologies / Mozilla.