smtpproxy is an application level gateway for SMTP. Features are optional ETRN support, POP3 before SMTP with pop3proxy, mail path removal, restrictions on allowed senders and recipients.
Open source project that offer summary and download services on this page is a project that carry out their development work on other open source development sites. Their work is linked to this page via a feature called OFI, and their work is not carried out here on OSDN site.