”Smart encoding” uses system settings (editable in the MisFox control panel supplied on the disk images advenced tab, or in Internet Explorer’s ”Receiving files/file helpers” preference pane) to determine if a file can be encoded using Base64 (if it does not contain essential information in the resource fork), or if it should be encoded using AppleDouble.

 Note that a .jpg file containing an icon and a preview in the resource fork will be sent in Base64 (so it will loose it’s icon and preview) when using ”smart encoding”, because it’s resource fork is not considered as essential information for a jpeg file. If you want to send a .jpg file with it’s icon and preview to mac users, but you want that windows users can also decode it, use AppleDouble (however, windows users will receive an additional unusable file that contain the resource fork).