Attachment not found in email window?

Attached an existing file in opportunity doctype.but i can not send attached file via mail,attached file not found in mail window.

What kind of file is that? Can you please try some other file also.

please refer attached is
screen shot for file details

You have added files from private folder, they will not show up for attachment others will.

any possibility to send private files from a doctype.i want to send files attached in another document

Only way right now is to upload them again and make sure Private is unchecked.