Sandboxing is a way to deliberately restrict applications accessing resources that they do not need to function properly. Sandboxing is intended to limit the effect of potential exploits and to mitigate overreach to personal data. Since June 1, 2012, sandboxing is a mandatory requirement for apps distributed through the Mac App Store (MAS). In addition, Apple has made it easier for developers to specify sandbox entitlements - capabilities that allow the app to access certain resources. However, sandboxing is still optional for macOS apps distributed outside Apple's official app store. This paper provides two contributions. First, the sandbox mechanism of macOS is analyzed and a critical sandbox-bypass is identified. Second, the general adoption of the sandbox mechanism, as well as app-specific sandbox configurations are evaluated. For that purpose all 8366 free apps of the MAS, making 25 % of all apps available on the MAS, as well as 4672 apps retrieved from MacUpdate (MU), a third-party app store, were analyzed dynamically. The dataset is over eight times larger than the second biggest study of macOS apps. It is shown that more than 94 % of apps on the MAS are sandboxed. However, more than 89 % of apps distributed through MU do not make use of sandboxing, putting users' data at risk.