Evolution does not automatically decrypt emails sent using the RFC 3156 standard

[jeremy-list]

To replicate: have someone send you an email encrypted with gpg using the RFC 3156 standard. An example mbox file is attached.
What I expect to happen: Evolution should prompt me for my private key passphrase and display the contents of the encrypted section inline.
What happened instead: The encrypted section was displayed as an attachment and I had to save and decrypt it manually.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: evolution 3.6.4-0ubuntu1
ProcVersionSignature: Ubuntu 3.8.0-30.44-generic 3.8.13.6
Uname: Linux 3.8.0-30-generic i686
ApportVersion: 2.9.2-0ubuntu8.3
Architecture: i386
Date: Tue Aug 27 22:17:32 2013
EcryptfsInUse: Yes
InstallationDate: Installed on 2011-08-09 (749 days ago)
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release i386 (20110427.1)
MarkForUpload: True
ProcEnviron:
 LANGUAGE=en_NZ:en
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_NZ.UTF-8
 SHELL=/bin/bash
SourcePackage: evolution
UpgradeStatus: Upgraded to raring on 2013-08-26 (1 days ago)