Read cron output with Thunderbird 91?

source: https://bugzilla.mozilla.org/show_bug.cgi?id=1625741

excerpt from comment 35...

Anyway, for whoever wants to know a slightly kludgy but likely "good enough" workaround, do this:

    - context-click on the "Local Folders" and find the "Local Directory" address
    - close thunderbird (maybe be paranoid and pgrep to ensure you don't have any persistent subprocess still running)
    - then create a symlink ln -s /var/mail/[SPOOL_FILE_NAME] /path/to/the/Local-Directory/address/you/found/above/Inbox (obviously ensure there isn't already an Inbox subfolder there, or otherwise create a differently named subfolder-symlink)

When I opened thunderbird it indexed it OK and after exiting and reopening thunderbird several times the symlink has stayed in place without problem.