YAM 2.5+ introduced a new so-called AttachmentGroup which shows all attachments of a mail in an icon/image bar at the bottom of the mail read window. For each attachment, it will show a seperate icon/image depending on the file type of the attachment. For archieving this, it uses the DefIcon system of the operating system it is runing on. This system allows (through SYS:Prefs/DefIcons) to configure seperate icons for various types of files. Unfortunately, it is limited and especially the way third-party applications like YAM can query the icon/image for a certain file isn't perfect at all. In addition, the way DefIcon identifies a file type is based on certain rules a user can configure in SYS:Prefs/DefIcons where some rules do actually try to analyze the binary content of the file in question and therefore require the actual file to exist.

Now, when YAM is going to show the user the AttachmentGroup, it hasn't decoded all different MIME parts due to performance reasons. This means, that at the time YAM tries to show the user the icon/image for an attachment, it just knows the filename, description and size of the attachment, but it hasn't actually written the binary data of it to disk. So, at the time YAM is going to ask the DefIcons system for the actual icon/image of the file it can't supply the decoded binary and therefore will only show/query for the default type based on the MIME type of the attachment.

However, as soon as the attachment was decoded either because it was viewed/printed/saved from within YAM, the AttachmentGroup will show the correct icon/image based on what DefIcons supplies.