ESMTP is a user-configurable relay-only MTA with a sendmail-compatible syntax,
based on libESMTP and supporting the AUTH (including the CRAM-MD5 and NTLM
SASL mechanisms) and StartTLS SMTP extensions. 

The doinst.sh script will create symlinks from /usr/sbin/sendmail and other
typical sendmail paths to /usr/bin/esmtp if sendmail is not already installed.

ESMTP requires LibESMTP, also available at SlackBuilds.org

NOTE: The esmtp package conflicts with the stock sendmail package - you must
      uninstall sendmail before installing esmtp.