Thunderbird ESR is here: Mozilla's email client adds new functions
(2025/07/09)
- Reference: 1752063312
- News link: https://www.theregister.co.uk/2025/07/09/new_thunderbird_esr_is_here/
- Source link:
The latest version of the messaging client from Mozilla subsidiary MZLA has a bunch of useful new features, and will get updated until mid 2026.
Firefox is fine. The people running it are not [1]READ MORE
[2]Thunderbird 140 "Eclipse" is not just an ordinary new version: it's the new Extended Support Release, which means that for the most cautious users this will be current until the middle of next year, and its packing some fresh functions.
The release follows [3]May's Thunderbird 139 , but it is not the same. As we covered when [4]Firefox and Thunderbird 138 came out , Thunderbird joined Firefox in its approximately monthly release schedule [5]back in February .
So now, for Thunderbird just like its sibling browser, there are two different and separate release channels: the slower-moving ESR channel, in which versions last for about a year and get just security fixes rather than new features, and the normal Release channel, which [6]MZLA recommends . New releases arrived about every four weeks, and they also get point releases between times if there are urgent bugs or security issues.
Thunderbird 140 is both: it's got some significant new features, but it will also get updated for the next year, until Thunderbird 152 or thereabouts. The announcement calls out five features for special attention.
[7]
Dark Message Mode applies the app's existing dark mode to message bodies as well, overriding emails' own formatting. This vulture rarely uses dark mode, but if you do presumably this sounds good. This version consolidates appearance preferences from several different places into the Appearance tab of the Settings screen, including making it easier to switch from the new Card view that [8]appeared in Thunderbird 115 to the traditional Table view. In Table view, it now supports horizontal scrolling.
[9]
[10]
The app now uses the host OS's native notifications on all three supported platforms, Windows, macOS and Linux, and allows you to act on messages direct from the new-message notification, such as archiving it or marking as read. Accounts management has been simplified and consolidated: adding any new account uses the new Account Hub wizard. Handily, folders can now be dragged to rearrange them without going into accounts settings.
One new feature that the Reg FOSS desk was really hoping to see has not arrived: we're still waiting for Thunderbird Sync, which we [11]mentioned in 2023 and seems no closer, despite the [12]occasional mention on the project blog.
[13]
This release's announcement also mentions a new feature which has been there for a while: desktop Thunderbird can [14]show a QR code which you can scan using Thunderbird for Android. This immediately recreates all the accounts from the desktop version. We tested this when we [15]looked at Murena /e/ OS 3 and it works very well. It's not as versatile as the equivalent to [16]Firefox Sync we had hoped for, but it's a good big stride in the right direction.
A feature that is flagged as being still experimental is direct Microsoft Exchange support. This has been [17]in development for quite some time. Thunderbird can already talk to Exchange servers: the problem is, it depends on how each specific Exchange box is configured. If Exchange's [18]optional IMAP4 support is installed and enabled, Thunderbird can use that on its own. However, Microsoft's own clients don't use standard protocols, so many sites don't have that.
[19]Neptune OS is Debian made easy but, boy, does it need some housekeeping
[20]Thunderbird joins Firefox on the monthly treadmill
[21]Ubuntu 25.04 beta takes flight – but this Plucky Puffin is still molting
[22]Mozilla is rolling Thundermail, a Gmail, Office 365 rival
If you don't mind paying for an inexpensive Thunderbird extension, another option is [23]Beonex's Owl addon, which adds Exchange Server support. If the Exchange server is configured to [24]allow browser access – sometimes called Exchange Web Services or Outlook Web Access (EWS or OWA) – then another Beonex tool, [25]ExQuilla can use that to get Thunderbird talking to it.
ExQuilla's days are numbered, because Thunderbird can now natively talk to EWS, meaning it can access Exchange Servers without IMAP support and without addons. This spells the end for Beonex's add-on, but that clock was ticking anyway: Microsoft plans to [26]turn off EWS support in October 2026 for the current versions of Microsoft 365 and Exchange Online. It is being turned off, along with [27]other Microsoft web APIs , to be replaced with Microsoft's next-gen Graph API, which by then will be [28]a full decade old .
The 2026 ESR version of Thunderbird is expected to arrive months before this Exchange feature goes away, so it has time to prove itself – and in any event, many sites will keep their older versions of Exchange around. ®
Bootnote
For those who are not so keen on the UI changes happening since Firefox "Supernova" (115), "Nebula" (128) and now "Eclipse" (140), then a new ESR release of Thunderbird means that a new release of Betterbird is coming. The beta of Betterbird 140 is [29]already available .
Get our [30]Tech Resources
[1] https://www.theregister.com/2025/07/08/firefox_isnt_dead/
[2] https://blog.thunderbird.net/2025/07/welcome-to-thunderbird-140-eclipse/
[3] https://www.theregister.com/2025/05/29/thunderbird_139/
[4] https://www.theregister.com/2025/04/30/firefox_thunderbird_138/
[5] https://blog.thunderbird.net/2025/02/thunderbird-desktop-release-channel-default-download/
[6] https://support.mozilla.org/en-US/kb/thunderbird-release
[7] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/applications&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2aG6SIlSstHF5tDqbwiRJFgAAAJM&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[8] https://www.theregister.com/2023/02/14/thunderbird_115_supernova_complete_overhaul/
[9] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/applications&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aG6SIlSstHF5tDqbwiRJFgAAAJM&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[10] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/applications&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33aG6SIlSstHF5tDqbwiRJFgAAAJM&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[11] https://www.theregister.com/2023/05/26/new_betas_of_firefox_and_tbird/
[12] https://blog.thunderbird.net/2024/10/thunderbird-annual-report-2023-2024/
[13] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/applications&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aG6SIlSstHF5tDqbwiRJFgAAAJM&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[14] https://support.mozilla.org/en-US/kb/thunderbird-android-import
[15] https://www.theregister.com/2025/06/19/murena_e_os_3/
[16] https://support.mozilla.org/en-US/kb/how-do-i-set-sync-my-computer
[17] https://blog.thunderbird.net/2024/04/adventures-in-rust-bringing-exchange-support-to-thunderbird/
[18] https://learn.microsoft.com/en-us/exchange/clients/pop3-and-imap4/configure-imap4
[19] https://www.theregister.com/2025/05/22/neptune_os/
[20] https://www.theregister.com/2025/04/30/firefox_thunderbird_138/
[21] https://www.theregister.com/2025/04/04/ubuntu_2504_beta/
[22] https://www.theregister.com/2025/04/02/thunderbird_pay_services/
[23] https://www.beonex.com/owl/
[24] https://learn.microsoft.com/en-us/troubleshoot/exchange/client-connectivity/set-up-web-access
[25] https://www.exquilla.com/
[26] https://techcommunity.microsoft.com/blog/exchange/retirement-of-exchange-web-services-in-exchange-online/3924440
[27] https://www.theregister.com/2023/09/07/outlook_rest_api_deprecation/
[28] https://www.theregister.com/2016/04/22/microsoft_hooks_up_more_powerful_web_addins_for_crossplatform_office/?page=2
[29] https://www.betterbird.eu/downloads/
[30] https://whitepapers.theregister.com/
Firefox is fine. The people running it are not [1]READ MORE
[2]Thunderbird 140 "Eclipse" is not just an ordinary new version: it's the new Extended Support Release, which means that for the most cautious users this will be current until the middle of next year, and its packing some fresh functions.
The release follows [3]May's Thunderbird 139 , but it is not the same. As we covered when [4]Firefox and Thunderbird 138 came out , Thunderbird joined Firefox in its approximately monthly release schedule [5]back in February .
So now, for Thunderbird just like its sibling browser, there are two different and separate release channels: the slower-moving ESR channel, in which versions last for about a year and get just security fixes rather than new features, and the normal Release channel, which [6]MZLA recommends . New releases arrived about every four weeks, and they also get point releases between times if there are urgent bugs or security issues.
Thunderbird 140 is both: it's got some significant new features, but it will also get updated for the next year, until Thunderbird 152 or thereabouts. The announcement calls out five features for special attention.
[7]
Dark Message Mode applies the app's existing dark mode to message bodies as well, overriding emails' own formatting. This vulture rarely uses dark mode, but if you do presumably this sounds good. This version consolidates appearance preferences from several different places into the Appearance tab of the Settings screen, including making it easier to switch from the new Card view that [8]appeared in Thunderbird 115 to the traditional Table view. In Table view, it now supports horizontal scrolling.
[9]
[10]
The app now uses the host OS's native notifications on all three supported platforms, Windows, macOS and Linux, and allows you to act on messages direct from the new-message notification, such as archiving it or marking as read. Accounts management has been simplified and consolidated: adding any new account uses the new Account Hub wizard. Handily, folders can now be dragged to rearrange them without going into accounts settings.
One new feature that the Reg FOSS desk was really hoping to see has not arrived: we're still waiting for Thunderbird Sync, which we [11]mentioned in 2023 and seems no closer, despite the [12]occasional mention on the project blog.
[13]
This release's announcement also mentions a new feature which has been there for a while: desktop Thunderbird can [14]show a QR code which you can scan using Thunderbird for Android. This immediately recreates all the accounts from the desktop version. We tested this when we [15]looked at Murena /e/ OS 3 and it works very well. It's not as versatile as the equivalent to [16]Firefox Sync we had hoped for, but it's a good big stride in the right direction.
A feature that is flagged as being still experimental is direct Microsoft Exchange support. This has been [17]in development for quite some time. Thunderbird can already talk to Exchange servers: the problem is, it depends on how each specific Exchange box is configured. If Exchange's [18]optional IMAP4 support is installed and enabled, Thunderbird can use that on its own. However, Microsoft's own clients don't use standard protocols, so many sites don't have that.
[19]Neptune OS is Debian made easy but, boy, does it need some housekeeping
[20]Thunderbird joins Firefox on the monthly treadmill
[21]Ubuntu 25.04 beta takes flight – but this Plucky Puffin is still molting
[22]Mozilla is rolling Thundermail, a Gmail, Office 365 rival
If you don't mind paying for an inexpensive Thunderbird extension, another option is [23]Beonex's Owl addon, which adds Exchange Server support. If the Exchange server is configured to [24]allow browser access – sometimes called Exchange Web Services or Outlook Web Access (EWS or OWA) – then another Beonex tool, [25]ExQuilla can use that to get Thunderbird talking to it.
ExQuilla's days are numbered, because Thunderbird can now natively talk to EWS, meaning it can access Exchange Servers without IMAP support and without addons. This spells the end for Beonex's add-on, but that clock was ticking anyway: Microsoft plans to [26]turn off EWS support in October 2026 for the current versions of Microsoft 365 and Exchange Online. It is being turned off, along with [27]other Microsoft web APIs , to be replaced with Microsoft's next-gen Graph API, which by then will be [28]a full decade old .
The 2026 ESR version of Thunderbird is expected to arrive months before this Exchange feature goes away, so it has time to prove itself – and in any event, many sites will keep their older versions of Exchange around. ®
Bootnote
For those who are not so keen on the UI changes happening since Firefox "Supernova" (115), "Nebula" (128) and now "Eclipse" (140), then a new ESR release of Thunderbird means that a new release of Betterbird is coming. The beta of Betterbird 140 is [29]already available .
Get our [30]Tech Resources
[1] https://www.theregister.com/2025/07/08/firefox_isnt_dead/
[2] https://blog.thunderbird.net/2025/07/welcome-to-thunderbird-140-eclipse/
[3] https://www.theregister.com/2025/05/29/thunderbird_139/
[4] https://www.theregister.com/2025/04/30/firefox_thunderbird_138/
[5] https://blog.thunderbird.net/2025/02/thunderbird-desktop-release-channel-default-download/
[6] https://support.mozilla.org/en-US/kb/thunderbird-release
[7] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/applications&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2aG6SIlSstHF5tDqbwiRJFgAAAJM&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[8] https://www.theregister.com/2023/02/14/thunderbird_115_supernova_complete_overhaul/
[9] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/applications&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aG6SIlSstHF5tDqbwiRJFgAAAJM&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[10] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/applications&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33aG6SIlSstHF5tDqbwiRJFgAAAJM&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[11] https://www.theregister.com/2023/05/26/new_betas_of_firefox_and_tbird/
[12] https://blog.thunderbird.net/2024/10/thunderbird-annual-report-2023-2024/
[13] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_software/applications&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44aG6SIlSstHF5tDqbwiRJFgAAAJM&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[14] https://support.mozilla.org/en-US/kb/thunderbird-android-import
[15] https://www.theregister.com/2025/06/19/murena_e_os_3/
[16] https://support.mozilla.org/en-US/kb/how-do-i-set-sync-my-computer
[17] https://blog.thunderbird.net/2024/04/adventures-in-rust-bringing-exchange-support-to-thunderbird/
[18] https://learn.microsoft.com/en-us/exchange/clients/pop3-and-imap4/configure-imap4
[19] https://www.theregister.com/2025/05/22/neptune_os/
[20] https://www.theregister.com/2025/04/30/firefox_thunderbird_138/
[21] https://www.theregister.com/2025/04/04/ubuntu_2504_beta/
[22] https://www.theregister.com/2025/04/02/thunderbird_pay_services/
[23] https://www.beonex.com/owl/
[24] https://learn.microsoft.com/en-us/troubleshoot/exchange/client-connectivity/set-up-web-access
[25] https://www.exquilla.com/
[26] https://techcommunity.microsoft.com/blog/exchange/retirement-of-exchange-web-services-in-exchange-online/3924440
[27] https://www.theregister.com/2023/09/07/outlook_rest_api_deprecation/
[28] https://www.theregister.com/2016/04/22/microsoft_hooks_up_more_powerful_web_addins_for_crossplatform_office/?page=2
[29] https://www.betterbird.eu/downloads/
[30] https://whitepapers.theregister.com/
Re: Once again
Liam Proven
> an iPad … plus a keyboard… covers almost all of what a MacBook can do, and costs less.
If you want that and are happy with it, go for it. I am quite fond of my MacBook, which is slim, fast, and most saliently, even after two years lasts a few days on a charge. (The keyboard and trackpad are horrible, though.) I would rather file my copy over dialup from MS-DOS than use an iPad for any kind of actual daily work.
Why no iOS? Because, I presume, it's hard. iOS browsers are wrappers around Safari. (AFAIK nothing has changed there.) Thunderbird is implemented inside Firefox, I would presume as a load of Javascript and maybe some XUL and stuff even now. You can't run Firefox on iOS. Yes, there is an app called Firefox, but it's a wrapper around Safari which lets you get at your bookmarks and things.
That's why there are no extensions:
https://support.mozilla.org/en-US/questions/1486487
Re: Once again
Like a badger
"one wonders why there isn't a Thunderbird for iOS/iPadOS"
Probably because so many Apple buyers are entirely happy with the Apple mail capabilities. If someone chooses to pay a good slug of money to get into Apple's walled garden, then generally speaking it makes sense that they would prefer the offerings from that company over FOSS software? So, why develop and support the one/two client versions needed for Apple customers, when the take up will be even lower than Thunderbird for other platforms?
Re: Once again
Mockup1974
It will still run iOS, even if a slightly less horrible version of it. I personally refuse to use an operating system where I can't install software without identifying myself to a Big Tech company.
(iOS only allows you to install apps from the App Store, and to do that you need to create an Apple account, and to do that you need to provide a phone number, and to get a phone number you need to link it to a government ID in most countries of the world [UK, US and Canada being notable exceptions].)
Mockup1974
So Dark Reader won't be necessary anymore?
Once again
no iPadOS/iOS support. The beta versions of iOS 26 and iPadOS 26 are out (Beta 3 dropped earlier this week) and on an iPad you get a windowing environment remarkably similar to macOS on a MacBook Air. Even old iPadOS software can use it, as is; I have several apps dating from as far back as 2011 which work seamlessly. They will never be updated at this late date, but they still work. One wonders why there isn't a Thunderbird for iOS/iPadOS. One really does.
Personally, I think that iPadOS 26 is going to destroy the sales of lower-end MacBooks, an iPad (not even an iPad Pro, just a regular iPad or iPad AIr) plus a keyboard, and not necessarily an Apple keyboard, covers almost all of what a MacBook can do, and costs less. Except, of course, that some software is not available for iPadOS. Like Thunderbird. The newer, bigger, iPads in particular are excellent laptop replacements. If the required software is available.
I repeat: one wonders why there isn't a Thunderbird for iOS/iPadOS. One really does.