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1 | dma for Debian |
2 | -------------- | |
3 | ||
5d58b856 | 4 | 1. Deferred delivery by default |
fa8d8158 | 5 | |
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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 |
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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 | ||
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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. | |
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34 | |
35 | 3. Double-bounce handling | |
36 | ||
6a311c5f | 37 | By default, the dma mail transfer agent does not attempt to handle double |
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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, | |
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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 |