US
RFC 8551: Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 4.0 Message Specification
https://www.rfc-editor.org/rfc/rfc8551
… capability to indicate the ability to receive CompressedData is described in [ RFC3274 ] and is the preferred method for compatibility. Step 1. The MIME entity to be compressed is prepared according to Section 3.1 . Step 2. The MIME entity and other required data are processed i…