The present invention provides is a file delivery system for transmitting files to recipients using email, which may be used with existing email infrastructures. High volumes of large file attachments may be handled by routing attachments independent of an associated email. An attachment distribution system extracts the attachments of emails at mail servers and routes them through a hosting server thereby alleviating server loading on the mail server. The system may be configured for delivery optimization, recipient authentication and delivery confirmation. The system examines emails flowing through a distributed network of mail servers, and may invoke attachment extraction based on configurable rules like attachment size and sender validity, and move the attachments over the Internet or Intranet to a remote server that is capable of delivering the attachments to the email recipients.