When a user tries to install SMS Magic workflow in sandbox the following error may occur.
Package SMS Magic Workflow Install Failed- "Error Message: The post install script failed"
This issue occurs when user is not having MASS EMAIL permission. This leads to failing the Post installation script and opposing the package from installation.
- Go to Quick Find/search in salesforce.
- Email Administration->Deliverability->Change access level to All email.
- then try to install the package.
The issue will be resolved.