* Citadel and your Systems Mail Transport Agent

The easy way to get citadel doing inbound Mail is 
to install the "citadel-mta" package. 

You however can use your default MTA to deliver mails
to citadel using a feature called LMTP (Local Mail
Transport) which is supported by Postfix, Exim and 
qpsmp.

Citadel will open its lmtp Unix Domain Socket in 
/var/run/citadel/lmtp.socket
This is where you need to point your other MTA at.



 * Citadel and Exim

Exim is able to do this; however, the Author of this 
writing doesn't use it, and thus provides you just with 
this Link to the exim documentation:

http://exim.inode.at/exim-html-3.20/doc/html/spec_17.html

(If you know more, input is welcome)



 * Citadel and Postfix

Postfix offers more than just LMTP. Postfix also enables 
you to use DICT-TCP in order to verify whether an email
will be deliverable rigt after the other mailserver told
yours whom it wants to send mail to.
Have a look at this sample main.cf for postfix:

# See /usr/share/postfix/main.cf.dist for a commented, more complete version 
smtpd_banner = $myhostname ESMTP $mail_name (Debian/GNU) 
biff = no 

# appending .domain is the MUA's job. 
append_dot_mydomain = no 

# Uncomment the next line to generate "delayed mail" warnings 
#delay_warning_time = 4h
myhostname = sample.citadel.org 
#alias_maps = hash:/etc/aliases 
#alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = mail.sample.citadel.org, sample.citadel.org 
#relayhost = mynetworks = 127.0.0.0/8 
mailbox_size_limit = 0 
recipient_delimiter = + 
inet_interfaces = all 
# ------------------------------------------------ 
# checking rules. 
# get rid of anything useless as early as possible. 
# * stage one: check if the user is there. 
# * stage two: check the source. is its helo valid? else buye. 
# * stage three: check the sender etc. 
# * stage four: check the open relay Database. hosts registered here won't be accepted. 
# * stage five: check the content by regex. won't accept Windows executables of any kind. 
# * stage six: Do virus checking. reject some more extensions. 
# * stage seven: deliver it to citadel via local transport 
# make it bite harder if wanted. unknown_local_recipient_reject_code = 550 
#unknown_address_reject_code = 550 
#unknown_client_reject_code = 550 
#unknown_relay_recipient_reject_code = 550 
#unknown_virtual_alias_reject_code = 550 
#unknown_virtual_mailbox_reject_code = 550 
#unknown_address_reject_code = 550 
#unknown_client_reject_code = 550 
#unknown_hostname_reject_code = 550 
#unverified_recipient_reject_code = 550 
#unverified_sender_reject_code = 550 
#unverified_recipient_reject_code = 550 
#
# nope. don't wanna know. 
bounce_notice_recipient =  
# replace 127.0.0.1 with the ip of your citadel server, and 777 with the port you made it open its dict-tcp server
# in doubt check with netstat -lnp
# telnet ip port
# 
smtpd_recipient_restrictions =
        tcp:127.0.0.1:777,
        reject_unauth_destination,
        reject_unauth_pipelining,
        reject_non_fqdn_sender,
        reject_non_fqdn_hostname,
        reject_invalid_hostname,
        reject_unknown_recipient_domain,
        reject_unknown_sender_domain,
        reject_unknown_hostname,
        reject_rbl_client list.dsbl.org,
        reject_rbl_client sbl-xbl.spamhaus.org,
        reject_rbl_client bl.spamcop.net,
        reject_rbl_client dnsbl.njabl.org,
        reject_rbl_client dnsbl.sorbs.net,
        reject_rbl_client l2.spews.dnsbl.sorbs.net,
        reject_rhsbl_client rhsbl.sorbs.net,
        reject_rhsbl_client bogusmx.rfc-ignorant.org,
        reject_rhsbl_sender rhsbl.sorbs.net,
        reject_rhsbl_sender bogusmx.rfc-ignorant.org,
        reject_rhsbl_sender dsn.rfc-ignorant.org
        reject
#if we deliver to citadel via lmtp, do it for example like that:
local_transport = lmtp:unix:/var/run/citadel/lmtp.socket
# check the output of netstat -lnp for your lmtp.sock location.


More informations on this issue can be found at:
http://www.citadel.org/doku.php/faq:installation:configuring_postfix_to_validate_email_addresses_against_a_citadel_server


 -- Wilfried Goesgens <w.goesgens@outgesourced.org>, Thu, 17 May 2007 19:10:39 +0200