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.