Thunderbird in Linux, for some reason, still does not understand GIO filesystems. If you have a network location connected in your file manager (such as Nautilus) you can browse around, copy files and so on – but Thunderbird cannot see those locations. In particular, it can’t attach files out of those locations, not can it save attachments to those locations. Luckily, gvfs
provides a workaround.
Accessing network shares from Thunderbird
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