Thunderbird 67.0 Beta 1

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

Known Issues

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