Thunderbird Beta Notes

Version 66.0beta, first offered to channel users on February 12, 2019

Check out "What’s New" and "Known Issues" for this version of Thunderbird below. As always, you’re encouraged to tell us what you think, or file a bug in Bugzilla. If interested, please see the complete list of changes in this release.

These release notes apply to Thunderbird version 66 beta 3 released March 8th, 2019.

What’s New

  • changed

    ADD-ON SUPPORT: Restartless add-ons continue to work if their authors have made the necessary minor adjustments. Non-restartless legacy add-ons using XUL overlays are only supported if add-on authors have adapted them. Apart from Lightning/Calendar there are a few that have been adapted, like "ThunderHTMLedit", "Compact Header" and "Signature Switch". Instaling legacy add-ons now requires a restart. Legacy add-ons can now specify an options page again.

  • changed

    DICTIONARY SUPPORT: Only WebExtension dictionaries are supported now. Please download new dictionaries from addons.mozilla.org since addons.thunderbird.net still provides "legacy" dictionaries compatible with Thunderbird 60 ESR. Note that Thunderbird 60.5 ESR can also handle WebExtension dictionaries.

  • changed

    Maildir now uses the message ID as file name and "eml" as file extension

  • fixed

    Tags set on IMAP folders sometimes not visible to other users

  • fixed

    Various theme fixes and improvements

Fixed in Beta 2

  • fixed

    On Windows, changed options not saved (issue introduced in beta 1)

  • fixed

    Problem with S/MIME certificate verification when receiving email from Outlook (issue introduced in beta 1)

  • fixed

    Partly reverted MAPI changes from Thunderbird 65 beta 4 to mitigate malfunction

Fixed in Beta 3

  • fixed

    Custom tag colors outside the prior fixed 10x7 matrix of HTML colors not working. Now any chosen color will work.

  • fixed

    On Windows, dragging message to the desktop or a folder is not working

  • fixed

    Fixed Windows installer with respect to MAPI DLLs and re-enabled MAPISendMailW which was disabled in beta 2.
    If files with non-ASCII characters in their name still cause a malfunction, use one of the following two alternative solutions:

    • Reset this registry entry
      HKLM\SOFTWARE\Clients\Mail\Mozilla Thunderbird - SupportUTF8 to 0. Also reset HKLM\SOFTWARE\Wow6432Node\Clients\Mail\Mozilla Thunderbird - SupportUTF8 if present.
    • On Windows 10, set the system code page to UTF-8 (beta feature, see Region Settings, system locale)

  • fixed

    Chat: Fixed XMPP authentication when using SASL

Known Issues

  • unresolved

    Due to changes in the Mozilla platform profiles stored on Windows network shares addressed via drive letters are now addressed via UNC

  • unresolved

    Spellcheck marks disappeared erroneously for words with an apostrophe (working in Thunderbird ESR)

  • unresolved

    Calendar: A localized version of Provider for Google Calendar not available at addons.thunderbird.net or the Mozilla FTP server. A US-English version can be downloaded here.

  • unresolved

    Chat: Twitter not working due to API changes at Twitter.com