Version 7.8.0p0 is available upstream. Please consider updating! It seems that version 7.8.0p0 is available upstream, while the latest version in the Gentoo tree is 7.7.0_p0. You think this warning is false? Read more about it here.
OpenSMTPD is an implementation of the server-side SMTP protocol as defined by RFC 5321, with some additional standard extensions. It allows ordinary machines to exchange e-mails with other systems speaking the SMTP protocol.