[people/ms/dma.git] / README.Debian

dma for Debian
--------------

1. Deferred delivery by default

The dma mail transfer agent may operate in two modes - immediate and
deferred.  In both cases, a new dma process is spawned for the delivery
of each outgoing message, and this process lives on until the message is
either successfully delivered or it times out after five days.

In immediate delivery mode, the new dma process is spawned as soon as
the message is submitted to the queue.  In deferred mode, which is
the default for the Debian package, the message is left in the queue
and will only be processed when dma is invoked separately with the "-q"
command-line option.  This is the preferred delivery mode - even though
there may be slight delays, the queue must still be processed periodically
anyway (if an immediate delivery is deferred, the message is still left
on the queue), so there's no harm done in always doing it that way.

Hence, the Debian package of dma installs a cron job that attempts to
flush the queue every five minutes.  Note that this does NOT mean that
message delivery will be attempted every five minutes!  Once the queue
is flushed, a separate dma instance is spawned for each still-unhandled
message, and it takes care of reasonable exponential back-off in case of
delivery problems.

2. Smarthost operation by default - needs to be configured!

After first installing dma, you need to configure it for proper operation -
whether it should deliver all outgoing e-mail messages through a single
smarthost or attempt to contact the remote mail servers directly.  This should
be configured through the debconf questions, but you may change the setting
using the SMARTHOST directive in the /etc/dma/dma.conf file.

3. Double-bounce handling

By default, the dma mail transfer agent does not attempt to handle double
bounces - it aborts the delivery with a critical syslog message.
This, combined with the Debian package's default of "flush the queue
every five minutes", may pose something of a strain on the mail server :)
Thus, the Debian version of dma adds a new feature - you may specify
an external program to handle double bounces with the DBOUNCEPROG 
directive in the /etc/dma/dma.conf file.  Also included is a sample
program, dbounce-simple-safecat, which uses the safecat utility to
copy the bounce message into a Maildir-structured storage,
/var/spool/mail/dma-bounces by default.  For the present, the copied file
still has the dma internal format, which is plain text, but is not really
a mailbox :)

 -- Peter Pentchev <roam@ringlet.net>  Mon, 21 Jun 2010 11:31:02 +0300
Commit	Line	Data
fa8d8158 PP	1	dma for Debian
	2	--------------
	3
5d58b856	4	1. Deferred delivery by default
fa8d8158	5
5d58b856 PP	6	The dma mail transfer agent may operate in two modes - immediate and
	7	deferred. In both cases, a new dma process is spawned for the delivery
	8	of each outgoing message, and this process lives on until the message is
	9	either successfully delivered or it times out after five days.
	10
	11	In immediate delivery mode, the new dma process is spawned as soon as
	12	the message is submitted to the queue. In deferred mode, which is
	13	the default for the Debian package, the message is left in the queue
	14	and will only be processed when dma is invoked separately with the "-q"
6a311c5f	15	command-line option. This is the preferred delivery mode - even though
5d58b856 PP	16	there may be slight delays, the queue must still be processed periodically
	17	anyway (if an immediate delivery is deferred, the message is still left
	18	on the queue), so there's no harm done in always doing it that way.
	19
	20	Hence, the Debian package of dma installs a cron job that attempts to
	21	flush the queue every five minutes. Note that this does NOT mean that
	22	message delivery will be attempted every five minutes! Once the queue
	23	is flushed, a separate dma instance is spawned for each still-unhandled
	24	message, and it takes care of reasonable exponential back-off in case of
	25	delivery problems.
	26
	27	2. Smarthost operation by default - needs to be configured!
	28
fd2815af PP	29	After first installing dma, you need to configure it for proper operation -
	30	whether it should deliver all outgoing e-mail messages through a single
	31	smarthost or attempt to contact the remote mail servers directly. This should
	32	be configured through the debconf questions, but you may change the setting
	33	using the SMARTHOST directive in the /etc/dma/dma.conf file.
5d58b856 PP	34
	35	3. Double-bounce handling
	36
6a311c5f	37	By default, the dma mail transfer agent does not attempt to handle double
5d58b856 PP	38	bounces - it aborts the delivery with a critical syslog message.
	39	This, combined with the Debian package's default of "flush the queue
	40	every five minutes", may pose something of a strain on the mail server :)
	41	Thus, the Debian version of dma adds a new feature - you may specify
	42	an external program to handle double bounces with the DBOUNCEPROG
	43	directive in the /etc/dma/dma.conf file. Also included is a sample
	44	program, dbounce-simple-safecat, which uses the safecat utility to
	45	copy the bounce message into a Maildir-structured storage,
6a311c5f PP	46	/var/spool/mail/dma-bounces by default. For the present, the copied file
	47	still has the dma internal format, which is plain text, but is not really
	48	a mailbox :)
5d58b856	49
fd2815af	50	-- Peter Pentchev <roam@ringlet.net> Mon, 21 Jun 2010 11:31:02 +0300