@hamann ah actually this bug is already fixed with https://git.cloudron.io/cloudron/box/-/commit/cefbe7064f4c7b31fb93bbf7ed85bf916aa5cf39 but pending a release.
For the meantime you could tweak the file manually at /home/yellowtent/box/src/apps.js and then systemctl restart box or enable the mailbox for that app temporarily.