You can not. They actually do not exist until they are opened of detached and saved somewhere. All attachments exist as MIME encoded text in the body of the email they arrived in, but they are not a "file" or really distinct data. A discrete part of the message body is marked as being the attachment. But that data has to be decoded to get to the actual binary file that was sent. So perhaps if you explained what it was you think you are trying to achieve we might be able to offer some ideas. Ideas like https://addons.thunderbird.net/en-US/thunderbird/addon/attachment-extractor/?src=ss