I recently moved away from my iPhone and am trialing a Galaxy S3.
After a lot of difficulty, I set up my .mac email on the S3 and all seemed to be working well.
But Mail on my Mac now has separate Sent and Trash Folders under iCloud, which only have the Sent and Trashed eMails from my S3. All eMails sent and Trashed from my Mac show up under the normal Folders.
When I had my iPhone, all Sent and Trash items - both from Mac Mail and iPhone Mail - showed up under Mailboxes Sent and Trash.