Thunderbird 145 finally adds ‘native’ Exchange support
(2025/11/20)
- Reference: 1763658485
- News link: https://www.theregister.co.uk/2025/11/20/thunderbird_microsoft_exchange_support/
- Source link:
It's easy to forget in the FOSS world, but Exchange still runs most corporate email – and the new version of Thunderbird can talk to it directly.
[1]Thunderbird 145 arrived around the same time as [2]Firefox 145 – and you may be pleased to hear that it does not boast Firefox's integrated AI features. On the day it was announced, it was [3]not yet available , but downloads (and upgrades for existing users) followed some days later.
As usual with the [4]new release cadence that MZLA has been following since April, the monthly releases are relatively modest, with lots of bug fixes — the release notes list 25 bugs fixed, plus a further [5]16 security fixes — and only one or two major features each time.
[6]
This time, though, the new feature is a pretty big one for a lot of people, and it merited its own MZLA blog post on November 18: [7]Thunderbird Adds Native Microsoft Exchange Email Support .
[8]
[9]
What the company means by "native" is that Thunderbird can now talk directly to [10]Microsoft's Exchange Web Services (or EWS for short). At this point, the Microsoft enthusiasts out there are probably shouting at their computers that EWS is deprecated and it's on its way out. Well, yes, it is, and has been [11]since 2018 . The Register [12]mentioned it back in 2020 … but as ever, the real story is a little more complicated than that.
Yes, EWS is deprecated, and Microsoft is currently saying that it will be [13]turned off from October 1 2026 – but this only applies to the hosted Exchange Online service. As the Microsoft announcement says:
the retirement of EWS apply only to Microsoft 365 and Exchange Online (all environments); there are no changes to EWS in Exchange Server.
For companies that run their own on-premises Exchange Servers, EWS isn't going anywhere. Furthermore, although the Reg FOSS desk is delighted that they don't personally have to support any Exchange Server instances anymore, we were still fettling ES 5.5 in 2002, and over a decade later, ES 2003 in 2013. The first version (ES 4.0) was released 29 years ago, and pretty much ever since the second release, ES 5.0, it's been common for companies to keep ancient and long-unsupported versions running.
For now, in this first version, the new support is limited to sending and receiving email, and searching via subject line and body text. Calendar and contacts support is coming in a future release, as well as custom sign-on agents, and eventually support for the new [14]Microsoft Graph API . The client-side stuff is already there: Thunderbird has had built-in calendar functionality since version 78, which is the same version that [15]incorporated PGP encryption support – thus rendering obsolete both the Enigmail and Lightning add-ons at once.
[16]
Customers who must have calendar and shared address book support still have other options, including existing Thunderbird Exchange add-ons such as [17]ExQuilla and [18]Beonex's Owl . Now there's integral EWS email support, there's also an opportunity for Beonex to offer MS Graph support before MZLA does, and thus keep Thunderbird talking to the Microsoft 365 version of Exchange.
[19]Thunderbird ESR is here: Mozilla's email client adds new functions
[20]Mozilla is rolling Thundermail, a Gmail, Office 365 rival
[21]Thunderbird 142 lands with modest upgrades – plus talk of Pro service ahead
[22]Thunderbird is go: 139 follows closely on Firefox's heels
MZLA is also still working on the forthcoming [23]Thunderbird Pro service, which as The Reg [24]reported back in April will include Thundermail, a service to rival Gmail and Office 365. It just published a [25]Thunderbird Pro November 2025 Update , and it's apparently now in internal testing. As well as existing protocols, Thunderbird Pro will also be available over [26]JMAP , the new JSON Meta Application Protocol. Now an IETF standard, JMAP is intended to be a successor to IMAP. JMAP combines email sending, receiving, storage and searching with calendaring and contacts handling, all in one account and one connection, offering the FOSS world a simpler rival to corporate groupware services.
For those keen to try the new EWS functionality but encountering problems, there's a [27]dedicated support page available. ®
Get our [28]Tech Resources
[1] https://www.thunderbird.net/en-US/thunderbird/145.0/releasenotes/
[2] https://www.theregister.com/2025/11/12/firefox_145_arrives/
[3] https://lwn.net/Articles/1046377/
[4] https://www.theregister.com/2025/04/30/firefox_thunderbird_138/
[5] https://www.mozilla.org/en-US/security/advisories/mfsa2025-90/
[6] 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=2aR-di5KtlylGDLC1lGLTnwAAAM0&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[7] https://blog.thunderbird.net/2025/11/thunderbird-adds-native-microsoft-exchange-email-support/
[8] 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=44aR-di5KtlylGDLC1lGLTnwAAAM0&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[9] 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=33aR-di5KtlylGDLC1lGLTnwAAAM0&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[10] https://learn.microsoft.com/en-us/exchange/client-developer/exchange-web-services/ews-applications-and-the-exchange-architecture
[11] https://techcommunity.microsoft.com/blog/exchange/upcoming-changes-to-exchange-web-services-ews-api-for-office-365/608055
[12] https://www.theregister.com/2020/06/12/microsoft_macos_outlook_changes/
[13] https://devblogs.microsoft.com/microsoft365dev/retirement-of-exchange-web-services-in-exchange-online/
[14] https://learn.microsoft.com/en-us/graph/use-the-api
[15] https://www.theregister.com/2020/09/18/mozilla_kills_send_thunderbird_pgp/
[16] 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=44aR-di5KtlylGDLC1lGLTnwAAAM0&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[17] https://exquilla.zendesk.com/hc/en-us
[18] https://www.beonex.com/owl/
[19] https://www.theregister.com/2025/07/09/new_thunderbird_esr_is_here/
[20] https://www.theregister.com/2025/04/02/thunderbird_pay_services/
[21] https://www.theregister.com/2025/08/22/thunderbird_142/
[22] https://www.theregister.com/2025/05/29/thunderbird_139/
[23] https://tb.pro/en-GB/
[24] https://www.theregister.com/2025/04/02/thunderbird_pay_services/
[25] https://blog.thunderbird.net/2025/11/thunderbird-pro-november-2025-update/
[26] https://jmap.io/
[27] https://support.mozilla.org/en-US/kb/thunderbird-and-exchange
[28] https://whitepapers.theregister.com/
[1]Thunderbird 145 arrived around the same time as [2]Firefox 145 – and you may be pleased to hear that it does not boast Firefox's integrated AI features. On the day it was announced, it was [3]not yet available , but downloads (and upgrades for existing users) followed some days later.
As usual with the [4]new release cadence that MZLA has been following since April, the monthly releases are relatively modest, with lots of bug fixes — the release notes list 25 bugs fixed, plus a further [5]16 security fixes — and only one or two major features each time.
[6]
This time, though, the new feature is a pretty big one for a lot of people, and it merited its own MZLA blog post on November 18: [7]Thunderbird Adds Native Microsoft Exchange Email Support .
[8]
[9]
What the company means by "native" is that Thunderbird can now talk directly to [10]Microsoft's Exchange Web Services (or EWS for short). At this point, the Microsoft enthusiasts out there are probably shouting at their computers that EWS is deprecated and it's on its way out. Well, yes, it is, and has been [11]since 2018 . The Register [12]mentioned it back in 2020 … but as ever, the real story is a little more complicated than that.
Yes, EWS is deprecated, and Microsoft is currently saying that it will be [13]turned off from October 1 2026 – but this only applies to the hosted Exchange Online service. As the Microsoft announcement says:
the retirement of EWS apply only to Microsoft 365 and Exchange Online (all environments); there are no changes to EWS in Exchange Server.
For companies that run their own on-premises Exchange Servers, EWS isn't going anywhere. Furthermore, although the Reg FOSS desk is delighted that they don't personally have to support any Exchange Server instances anymore, we were still fettling ES 5.5 in 2002, and over a decade later, ES 2003 in 2013. The first version (ES 4.0) was released 29 years ago, and pretty much ever since the second release, ES 5.0, it's been common for companies to keep ancient and long-unsupported versions running.
For now, in this first version, the new support is limited to sending and receiving email, and searching via subject line and body text. Calendar and contacts support is coming in a future release, as well as custom sign-on agents, and eventually support for the new [14]Microsoft Graph API . The client-side stuff is already there: Thunderbird has had built-in calendar functionality since version 78, which is the same version that [15]incorporated PGP encryption support – thus rendering obsolete both the Enigmail and Lightning add-ons at once.
[16]
Customers who must have calendar and shared address book support still have other options, including existing Thunderbird Exchange add-ons such as [17]ExQuilla and [18]Beonex's Owl . Now there's integral EWS email support, there's also an opportunity for Beonex to offer MS Graph support before MZLA does, and thus keep Thunderbird talking to the Microsoft 365 version of Exchange.
[19]Thunderbird ESR is here: Mozilla's email client adds new functions
[20]Mozilla is rolling Thundermail, a Gmail, Office 365 rival
[21]Thunderbird 142 lands with modest upgrades – plus talk of Pro service ahead
[22]Thunderbird is go: 139 follows closely on Firefox's heels
MZLA is also still working on the forthcoming [23]Thunderbird Pro service, which as The Reg [24]reported back in April will include Thundermail, a service to rival Gmail and Office 365. It just published a [25]Thunderbird Pro November 2025 Update , and it's apparently now in internal testing. As well as existing protocols, Thunderbird Pro will also be available over [26]JMAP , the new JSON Meta Application Protocol. Now an IETF standard, JMAP is intended to be a successor to IMAP. JMAP combines email sending, receiving, storage and searching with calendaring and contacts handling, all in one account and one connection, offering the FOSS world a simpler rival to corporate groupware services.
For those keen to try the new EWS functionality but encountering problems, there's a [27]dedicated support page available. ®
Get our [28]Tech Resources
[1] https://www.thunderbird.net/en-US/thunderbird/145.0/releasenotes/
[2] https://www.theregister.com/2025/11/12/firefox_145_arrives/
[3] https://lwn.net/Articles/1046377/
[4] https://www.theregister.com/2025/04/30/firefox_thunderbird_138/
[5] https://www.mozilla.org/en-US/security/advisories/mfsa2025-90/
[6] 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=2aR-di5KtlylGDLC1lGLTnwAAAM0&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[7] https://blog.thunderbird.net/2025/11/thunderbird-adds-native-microsoft-exchange-email-support/
[8] 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=44aR-di5KtlylGDLC1lGLTnwAAAM0&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[9] 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=33aR-di5KtlylGDLC1lGLTnwAAAM0&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[10] https://learn.microsoft.com/en-us/exchange/client-developer/exchange-web-services/ews-applications-and-the-exchange-architecture
[11] https://techcommunity.microsoft.com/blog/exchange/upcoming-changes-to-exchange-web-services-ews-api-for-office-365/608055
[12] https://www.theregister.com/2020/06/12/microsoft_macos_outlook_changes/
[13] https://devblogs.microsoft.com/microsoft365dev/retirement-of-exchange-web-services-in-exchange-online/
[14] https://learn.microsoft.com/en-us/graph/use-the-api
[15] https://www.theregister.com/2020/09/18/mozilla_kills_send_thunderbird_pgp/
[16] 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=44aR-di5KtlylGDLC1lGLTnwAAAM0&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[17] https://exquilla.zendesk.com/hc/en-us
[18] https://www.beonex.com/owl/
[19] https://www.theregister.com/2025/07/09/new_thunderbird_esr_is_here/
[20] https://www.theregister.com/2025/04/02/thunderbird_pay_services/
[21] https://www.theregister.com/2025/08/22/thunderbird_142/
[22] https://www.theregister.com/2025/05/29/thunderbird_139/
[23] https://tb.pro/en-GB/
[24] https://www.theregister.com/2025/04/02/thunderbird_pay_services/
[25] https://blog.thunderbird.net/2025/11/thunderbird-pro-november-2025-update/
[26] https://jmap.io/
[27] https://support.mozilla.org/en-US/kb/thunderbird-and-exchange
[28] https://whitepapers.theregister.com/
Re: MZLA
ThomH
I initially wondered the same until I found out that MZLA is a legal subsidiary of Mozilla that is responsible for Thunderbird. So it's a separate entity, to an extent.
Why was this page unavailable ?
Anonymous Coward
Got a 404 until I went through the survey.
Coincidence or bad layout?
MZLA
Why are you referring to Mozilla as MZLA all of a sudden? It makes no sense