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
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