Error Message: "First error: SendEmail failed. First exception on row 0; first error: NO_MASS_MAIL_PERMISSION, Single email is not enabled for your organization or profile"
An error stating "NO_MASS_MAIL_PERMISSION" can occur when converting an opportunity to a sales invoice. This error indicates that the user lacks the necessary permissions for mass email functionality. To resolve this, a system administrator must adjust settings related to mass email deliverability, tab access, and user permission sets. Proper configuration ensures users can send emails as required.