<!--
{
  "availability" : [
    "macCatalyst: 13.0.0 -",
    "macOS: 10.0.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "Security",
  "identifier" : "/documentation/Security/CMSSignedAttributes/attrSmimeMSEncryptionKeyPrefs",
  "metadataVersion" : "0.1.0",
  "role" : "Type Property",
  "symbol" : {
    "kind" : "Type Property",
    "modules" : [
      "Security"
    ],
    "preciseIdentifier" : "c:@E@CMSSignedAttributes@kCMSAttrSmimeMSEncryptionKeyPrefs"
  },
  "title" : "attrSmimeMSEncryptionKeyPrefs"
}
-->

# attrSmimeMSEncryptionKeyPrefs

Indicate that the signing certificate included with the message is the preferred one for S/MIME encryption, but using an attribute object identifier (OID) preferred by Microsoft.

```
static var attrSmimeMSEncryptionKeyPrefs: CMSSignedAttributes { get }
```

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)