The attachments are part of outlook on Windows computer. They are not available as separate files. So
RecentX cannot see them.
If you open the attachment, you may see it in
RecentX . This is not always the case since Outlook opens the attachment in temporary folder and may later delete the file from temporary folder.
RecentX does index files from temporary folder too. But it doesn't pick immediately because temporary folder is used by several applications just to create temporary files the user is not interested in.
However, if you save the attachment explicitly to a folder from Outlook and then open it, you should see it in
RecentX immediately.