SlackBuildsOrg/libraries/libesmtp

LibESMTP is a library to manage posting (or submission of) electronic mail
using SMTP to a preconfigured Mail Transport Agent (MTA) such as Exim. It may
be used as part of a Mail User Agent (MUA) or another program that must be
able to post electronic mail but where mail functionality is not the
program's primary purpose.  LibESMTP is not intended to be used as part of a
program that implements a Mail Transport Agent.