Advanced Exchange settings for iOS consist of S/MIME and Security configuration options, providing user-specific, certificate-based encryption of email.

Setting Description
Use S/MIME Use Secure Multipurpose Internet Mail Extensions, a public key encryption and signing standard.
S/MIME Certificate Only available when Use S/MIME is enabled. Add a signing certificate to emails by selecting Add A Certificate.
S/MIME Encryption Certificate Only available when Use S/MIME is enabled. Add a certificate that encrypts and digitally signs email by selecting Add A Certificate.
Enable Per-Message Switch Only available when Use S/MIME is enabled. Allow end users to choose which individual email messages to sign and encrypt using the native iOS mail client (iOS 8+ supervised only).
Settings and Security
Prevent moving messages Prevent moving mail from an Exchange mailbox to another mailbox on the device.
Prevent use in third-party apps Prevent other apps from using the Exchange mailbox to send messages.
Prevent Recent Address syncing Prevent suggestions for contacts when sending mail in Exchange.
Prevent Mail Drop Prevent Apple's Mail Drop feature from being used.