Nudity scanning for Gmail attachments is a premium feature from Securly that can be turned on by signing up for Auditor+. 

If you are an existing Auditor user, please navigate to your Securly portal and click the ‘Get Started with Auditor+’ button in your Auditor tab. You will be guided through a 5-minute installation process at the end of which we will start scanning Gmail attachments for nudity. 

Please ensure that you uncheck the ‘Remove attachments from message’ field from the Auditor route in your G Suite. Without this, the Auditor server will not receive any Gmail attachments to scan for nudity.