Thunderbird already can support Calendars and Contacts from Nextcloud through Caldav and Carddav.
In my dreams Thunderbird should be natively able to:
- pick attachments from Nextcloud Files and produce a link to the resource or a real attachment from there
- save .eml and/or attachments to Nextcloud Files directly
- embed a Nextcloud Talk client in instant messaging tab
- share Contacts/Calendars directly from Nextcloud and auto-refresh calendar list when new ones are shared to me.
Doing this, Thunderbird + Nextcloud + Dovecot/Postfix could replace Outlook/Exchange or M$365 in office environment.