The Thunderbird development team has delayed the release of Thunderbird 38 for about two weeks. Below was posted on the mozillaZine Thunderbird Builds forum on Monday:
from tb-planing mailing list :R Kent James wrote:
Thunderbird 38.0 will not ship on the same date as Firefox 38.0 but will likely be delayed a couple of weeks.We are approaching the originally scheduled date of the release of Thunderbird 38, which would be May 12 following the standard Mozilla release calendar. But there are still a number of regressions that we are working on, and last week’s beta was the first beta that was feature complete. That means we will not be ready to ship according to the original schedule. A current estimate of when we will ship Thunderbird 38.0 is approximately May 26.