Mozilla released the next update to the Thunderbird 38 branch on December 23rd with Thunderbird 38.5 release. There were some minor fixes with this update:
- In the address book manager, make the contacts sidebar remember the last selected address book (1142705)
- Prepare to use SHA-256 signing certificate for Windows builds, to meet new signing requirement (1079858)
- Various security fixes
Depending on their update settings, users will be prompted soon to update to the newest version of Thunderbird. Users may trigger the update from within Thunderbird via Help > About Thunderbird and following the prompts. Also, users can maually download and install the newest version of Thunderbird via the getthunderbird.com site. The next scheduled release will be Thunderbird 38.6.0 in late January early February 2016.