Thunderbird 67.0 Beta 3

Thunderbird

Thunderbird is a free, open-source, cross-platform application for managing email and news feeds. It is a local (rather than a web-based) email application that is powerful yet easy-to-use. Thunderbird is developed, tested, translated and supported by the folks at Mozilla Corporation and by a group of dedicated volunteers. Thunderbird gives you control and ownership over your email. There are lots of add-ons available for Thunderbird that enable you to extend and customize your email experience.

Thunderbird gives you IMAP/POP support, a built-in RSS reader, support for HTML mail, powerful quick search, saved search folders, advanced message filtering, message grouping, labels, return receipts, smart address book LDAP address completion, import tools, and the ability to manage multiple e-mail and newsgroup accounts.

What’s changed in Thunderbird 67.0 Beta 1:

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", "Signature Switch" and "Send Later".
DICTIONARY SUPPORT: Only WebExtension dictionaries are supported now. Both addons.mozilla.org and addons.thunderbird.net now provide WebExtension dictionaries.
Improvements when entering, selecting and removing recipients in the Write window

Changed and fixed in Beta 2:

Attachment pane of Write window no longer focussed when attaching files using a keyboard shortcut
Fixed - Navigation of attachments in Write window
Fixed - Insufficient contrast between forground and background colors for some tagged messages

Known Issues

Customising From address breaks saving draft and sending message
Malfunction when deleting a message opened in a tab or stand-alone window
Thunderbird 67 beta may not recognise an existing profile. Workaround: start with the profile manager option -p.
Thunderbird 67 beta may display a message "You've launched an older version of Firefox" and will not allow opening a specific profile. Workaround: start with option --allow-downgrade.
Due to changes in the Mozilla platform profiles stored on Windows network shares addressed via drive letters are now addressed via UNC
Spellcheck marks disappeared erroneously for words with an apostrophe (working in Thunderbird ESR)
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. The XPI file needs to be installed manually in Thunderbird.
Chat: Twitter not working due to API changes at Twitter.com

Thunderbird 67.0 Beta 3 changelog:

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", "Signature Switch" and "Send Later".
DICTIONARY SUPPORT: Only WebExtension dictionaries are supported now. Both addons.mozilla.org and addons.thunderbird.net now provide WebExtension dictionaries.
Improvements when entering, selecting and removing recipients in the Write window