The next major version of Thunderbird (Thunderbird 60) will be available in 64-bit. It is scheduled to be released somewhere in May 2018.

''Onno Ekker [[#answer-1069367|said]]'' <blockquote> The next major version of Thunderbird (Thunderbird 60) will be available in 64-bit. </blockquote> Any information to back this up? that is if you mean for 64-bit Windows as there is already 64-bit Thunderbird for Mac OSX and Linux for a long while now because it was needed. Only the unstable Nightly channel has had Win64 builds (currently 60.0a1) for QA testing reasons much like was the case for Firefox for a long time before going through the channels to eventually be considered stable for Release as of Firefox 42.0. There are Tb 58.0b1, 58.0b2, 58.0b3 Beta builds and only as 32-bit for Windows as there is no Win64 builds. Would make sense to have Win64 builds of Tb 58.0 Beta builds in Testing in meantime this close to 60.0. The Tb 57.0b1, 57.0b2 Beta builds were only as 32-bit for Windows also. https://ftp.mozilla.org/pub/thunderbird/releases/58.0b3/ https://ftp.mozilla.org/pub/thunderbird/nightly/latest-comm-central/ (Win64 builds of 58.0a1, 59.0a1, 60.0a1) edit: nothing about Win64 Thunderbird 60.0 in [https://bugzilla.mozilla.org/show_bug.cgi?id=634233 Bug 634233] - [Tracking meta bug] officially support Windows 64-bit builds in Thunderbird For people not familiar with how to use Bugzilla the above tracking Bug is for reading and is not a discussion forum like here. https://bugzilla.mozilla.org/page.cgi?id=etiquette.html