Thank you for updating the .desktop file. The issue is more hairy than it seems at first glance. E.g. https://debbugs.gnu.org/ sends "Content-disposition" header with ".mbox" suffix when a single comment in mbox format is requested (to reply to particular message). Thunderbird believes that a suitable action is to compose a new message with downloaded file as an attachment.
There is no command line option to force thunderbird to open a file as namely mail message. The position of developers is that such file must have ".eml" extension otherwise it is not a message. See https://bugzilla.mozilla.org/show_bug.cgi?id=1755454 for details (bug title has been changed to fix a loosely related issue). ** Bug watch added: Mozilla Bugzilla #1755454 https://bugzilla.mozilla.org/show_bug.cgi?id=1755454 -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to thunderbird in Ubuntu. https://bugs.launchpad.net/bugs/1861262 Title: Add message/rfc822 to thunderbird.desktop Status in thunderbird package in Ubuntu: Fix Released Bug description: Please add message/rfc822 to thunderbird.desktop: -MimeType=x-scheme-handler/mailto;application/x-xpinstall; +MimeType=x-scheme-handler/mailto;application/x-xpinstall;message/rfc822; It will allow to open *.eml files. I attach an example eml file. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/thunderbird/+bug/1861262/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
