Drag Outlook emails to a desktop folder. You may choose certain messages and drag them to a folder in Windows Explorer (or Finder on a Mac) if you don't want to store the full collection. By doing this, all emails—along with any attachments—are saved as separate.MSG files with the topic as the filename. These messages can only be reopened in Outlook for Windows; other email clients are unable to do so due to Outlook's exclusive.MSG file structure