It's currently rather difficult to display the mime-part tree as it is presented because what's exported doesn't reflect what needs to be displayed.
For instance:
```
MimeMesssgePart isAttachment
CryptoMessagePart isAttachment
CryptoMessagePart isAttachment
TextMessagePart isAttachment
MessagePart (main body)
TextMessagePart isAttachment
MessagePart (signed encrypted attachment)
CryptoMessagePart isAttachment
TextMessagePart isAttachment
MessagePart (unsigned encrypted attachment)
```
This results in a ridiculous amount of nested views that do absolutely nothing.
Also, we can't filter out attachments, because everything that isn't directly a text part is an attachment it seems.
What we need is this:
```
Message
Text (main body, encrypted, signed)
Attachment (encrypted, signed)
Attachment (encrypted)
```
So rather a fairly flat tree, with properties to figure out what is now signed or encrypted.
In most cases a list should be good enough, in some cases some hierarchical information may be useful to be able to display some thing inline.