Friday, April 9, 2010

Setting up QMQP

QMQP is faster than SMTP. You can use QMQP to send mails from your relay servers to a server running QMQP service. The QMQP service can deliver mails to your local mailboxes or/and relay mails to the outside world.

Client Setup

QMQP provides a centralized mail queue within a cluster of hosts. QMQP clients do not require local queue for queueing messages. For a minimal QMQP client installation, you need to have the following
  • forward, qmail-inject, sendmail, predate, datemail, mailsubj, qmail-showctl, maildirmake, maildir2mbox, maildirwatch, qail, elq, and pinq in /var/indimail/bin;
  • All files in /var/indimail/lib;
  • a symbolic link to qmail-qmqpc from /var/indimail/bin/qmail-queue;
  • symbolic links to /var/indimail/bin/sendmail from /usr/sbin/sendmail and /usr/lib/sendmail;
  • all the manual pages in /var/indimail/man;
  • a list of IP addresses of QMQP servers, one per line, in /var/indimail/control/qmqpservers;
  • a copy of /var/indimail/control/me, /var/indimail/control/defaultdomain, and /var/indimail/control/plusdomain from your central server, so that qmail-inject uses appropriate host names in outgoing mail; and
  • this host's name in /var/indimail/control/idhost, so that qmail-inject generates Message-ID without any risk of collision.
Everything can be shared across hosts except for /var/indimail/control/idhost.

Remember that users won't be able to send mail if all the QMQP servers are down. Most sites have two or three independent QMQP servers.

Note that users can still use all the qmail-inject environment variables to control the appearance of their outgoing messages.

If you want to setup a SMTP service, it might be easier to install the entire IndiMail package and remove the services qmail-send.25, indisrvr.4000, proxy-imap*, proxy-pop3*, qmail-imap*, qmail-pop3*, qmail-qm*. You can use svctool to remove the service e.g.

% sudo /var/indimail/sbin/svctool --rmsvc qmail-send.25

In case the mails generated by the client is to be relayed to the outside world, you should set the SMTP service and have /usr/sbin/sendmail, /usr/lib/sendmail linked to /var/indimail/bin/sendmail.sh. This is to ensure that tasks like virus scanning, dk, dkim signing happen at the client end. You can also choose not to have these tasks done at the client end, but rather have it carried out by the QMQP service.

QMQP Service

IndiMail runs a QMQP service which handles incoming QMQP connections on port 628 using tcpserver. It uses multilog to store log messages under /var/log/indimail/qmqpd.628

If you have installed IndiMail using the RPM, QMQP service is installed by default. However, you need to enable it.

% sudo /bin/rm /service/qmail-qmqpd.628/down
% sudo /var/indimail/bin/svc -u /service/qmail-qmqpd.628

If you have installed IndiMail using the source, you may create the QMQP service using the following command

% sudo /var/indimail/sbin/svctool --qmqp=628 --servicedir=/service \
--qbase=/var/indimail/queue --qcount=5 --qstart=1 \
--cntrldir=control --localip=0 --maxdaemons=75 --maxperip=25 \
--fsync --syncdir --memory=104857600 --min-free=52428800


The above command will create a supervised service which runs qmail-qmqpd under tcpserver. In case you are setting up this service to relay mails to outside world, you might want to also specify --dkfilter, --qhpsi, --virus-filter, etc arguments to svctool(8) so that tasks like virus scanning, dk, domainkey signing, etc is done by the QMQP service.

A QMQP server shouldn't even have to glance at incoming messages; its only job is to queue them for qmail-send(8). Hence you should allow access to QMQP service only from your authorized clients. You can edit the file /var/indimail/etc/tcp.qmqp to grant specific access to clients. If you make changes to tcp.qmqp, don't forget to run the qmailctl command

% sudo /var/indimail/bin/qmailctl cdb

Note: Some of the tasks like virus/spam filtering, dk, dkim signing, etc can be done either by the client (if QMAILQUEUE=/var/indimail/bin/qmail-multi), or can be performed by QMQP service if QMAILQUEUE is defined as qmail-multi in the service's variable directory.
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