Citadel is a turnkey open-source solution for email and collaboration. It contains both the server and a text-mode client. You can build an entire working system with this, or you can just build the client and connect to some other existing system. It also provides connectivity through: * SMTP (Port 25 by default) * POP3 (Port 110 by default; SSL Enabled on port 995) * IMAP (Port 143 by default; SSL Enabled on port 993) * Citadel (Port 504; used by dedicated Citadel clients) * SMTP-MSA (Port 587; requires SMTP authentication) * ManageSieve (Port 2020; edit your mail filtering scripts with your favorite GUI client) * Postfix TCP dictionary (if you have an upstream mail hub running Postfix, it can use this service to verify valid email addresses on your Citadel) * lmtp.socket (Local mail transport, for use with an external MTA if for some reason you do not wish to use Citadel's built in SMTP service) * lmtp-unfiltered.socket (same as above, but without spam filtering) * citadel.socket (Citadel protocol) After installation, run /opt/citadel/setup to configure Citadel. Dependencies: libsieve libcitadel Both available from slackbuilds.org