- Thunderbird ESR 24.0.1
- Thunderbird 24.0.1
- Thunderbird 26 Beta (25.0b1)*
- Thunderbird 27 Earlybird (26.0a2)*
- Thunderbird ESR 24.0.2
- Thunderbird 24.0.2
- Thunderbird 27 Beta (27.0b1)*
- Thunderbird 28 Earlybird (28.0a2)*
* As part of the new Rapid Release Schedule,dates listed for Earlybird and Beta builds reflect when the code merge is set to begin. The actual release to that particular channel may vary by several days.
Hmm, no more betas have been released since 27.0b1 on Dec. 19th. Mozilla wiki (https://wiki.mozilla.org/Releases#Based_on_Gecko_28) says 28 beta is current (since Feb. 4th?).