They scan everything- you have some settings in admin you can tweak. Scanning looks for spam and phishing- attachments may be scanned for malware - you can ena

They scan everything- you have some settings in admin you can tweak. Scanning looks for spam and phishing- attachments may be scanned for malware - you can enable enhanced pre delivery scanning. They don’t scan suite emails for ads. If you want to let stuff through you can setup an mx proxy and then whitelist the ip in admin settings. Just be ready for the metric ton of spam and scam emails you’ll get