Thunderbird takes up a large amount of disk space

According to my email provider, my mailbox is 5.2 GB in size. However, according to the Disk Usage Analyser, Thunderbird uses 9.6 GB.

I use Thunderbird with this my email provider (posteo.de) in a debian vm. But the problem also occurs in a fedora vm. Interestingly, the problem does not occur with another email provider (in this case also Thunderbird in a fedora vm).

Any ideas?

This doesn’t look a problem related to Qubes OS. You should probably ask on Thunderbird forums.

Okay, will do. Thanks.

Try compacting folders: Compacting folders | Thunderbird Help