in the latest version of the Files plugin, it’s not possible to add attachments to Emails anymore. I think I tracked it down to the fact that the files are not being downloaded from the Backend (in our case Owncloud/Nextcloud). It seems to have been caused by this commit: https://stash.kopano.io/projects/KWA/repos/files/diff/php/class.filesbrowsermodule.php?until=6d3d8898d734089dff72786050c2def86386cc6c
I think the missing of the get_file is causing the bug.
I tested the following fix and it works again for us:
$parts = explode('/', $file); array_shift($parts); $initializedBackend->get_file(implode('/', $parts), $tmpname);
Would be nice to have that working again. Thanks.