I’m sorry about that! I suspect that change to mailbox.twig should be fine, but worth keeping tabs on to make sure its not overwritten in a future update to mailcow.
When I check for container drive mappings for ./data/web*, not many come up. A couple containers have the entire ./data/web directory mapped, while some others only have specific files from within it mapped.
grep “./data/web” docker-compose.yml
Based on the filename you shared, looks like Mailcow’s UI is built in part on the PHP Twig template system:
I mention Twig since its use would have a higher chance of being overwritten in a future update.
Perhaps submit an issue in GitHub to request an enhancement to modify these default values?