E-mail attachments

In the form, I have four "file upload" elements. When I submit form, only the first document been attach in email. In Attachment fields in Email section i put: input_file_73 , input_file_74 , input_file_75 , input_file_76
Field name and Field ID is the same "input_file_7X"
After submit, all documents are in upload folder on server, but only first attach in email!

Thank you!🙂))