1MAILDIRQUOTA(7)             Double Precision, Inc.             MAILDIRQUOTA(7)
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NAME

6       maildirquota - voluntary Maildir quotas
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SYNOPSIS

9       maildirmake {-q} {10000000S} {./Maildir}
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DESCRIPTION

12       maildrop has a manual quota enforcement implementation that does use
13       the quota facilities of the host operating system (filesystem-based
14       quotas). This is an option that is set at configuration time, and may
15       be disabled.
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17       Using filesystem quotas sometimes leads to problems. After a hard quota
18       is hit, most commands issued by mail clients fail, including some
19       commands that poorly-written mail software may not expect to fail, and
20       therefore be unable to gracefully handle the unexpected failure.
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22       With manual quotas, the only operations that fail are the ones that
23       most mail clients expect to fail, when the mailbox is full. However,
24       filesystem-based quotas cannot be used in some situations, such as
25       virtual mailboxes. If this experimental feature is enabled, approximate
26       quota enforcement can be implemented by maildrop or deliverquota to
27       whatever extent it's possible to do so. Quotas are enabled by the -q
28       option to maildirmake. Both maildrop and deliverquota will observe any
29       maildirmake-requested quota.
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31   LIMITATIONS
32       This quota mechanism will only work as long as maildrop (or
33       deliverquota) are the only applications that deliver messages to the
34       maildir, or as long as other applications implement the same quota
35       enforcement mechanism. The quota enforcement mechanism is described
36       separately in the README.maildirquota.html file in the source code
37       distribution.
38
39       Quota enforcement will still work, to some extent, if there are other
40       applications that deliver or modify messages in the maildir. However,
41       quota enforcement may not kick in immediately when the maildir goes
42       over quota, in fact the maildir can go over quota by a noticeable
43       amount. But eventually, as long as maildrop or deliverquota are
44       responsible for delivering the majority of messages, quota enforcement
45       will kick in. Also, other sources of messages may also result in
46       noticeable performance degradation, because quote recalculation will
47       become noticeably more expensive.
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49       Also keep in mind that this quota mechanism is generally useless if
50       mail recipients have direct access to their maildirs.
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52       Finally even under the best conditions this quota enforcement does have
53       a small chance of a race condition where a maildir will go over quota
54       by some amount. maildirs are designed for speed, and this quota
55       implementation was designed to have as little additional overhead as
56       possible, compared to regular maildirs. To enforce an exact quota you
57       would have to use some kind of a locking facility, which will impose a
58       drastic performance degradation on the overall maildir performance. A
59       decision has been made to avoid locking, with the only negative side
60       effect being a possibility of going over quota in very low probability
61       situations.
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63       A way to minimize the risk of going over quota is to set reasonable
64       quotas, in relation to maximum message sizes supported by your mail
65       server. If you set your maildir quota to five gigabytes, for example,
66       it makes very little sense to configure your mail server to accept
67       messages up to three gigabytes in size. Your maildir quota should be
68       chosen so that it makes sense when compared to the maximum message size
69       allowed by your mail server.
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71   FOLDERS
72       This quota implementation is compatible with a popular extension to
73       maildir which defines individual mail folders within a single maildir.
74       However, in order to create a compatible folder, you MUST use the
75       maildirmake command that comes with maildrop, and you MUST use the -f
76       option to maildirmake, giving the name of the folder. Do not use
77       maildirmake and specify the directory name of the maildir folder. Quota
78       enforcement will not work if you do that.
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SEE ALSO

81       maildrop(1)[1], maildirmake(1)[2], maildropfilter(5)[3],
82       deliverquota(8)[4].
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AUTHOR

85       Sam Varshavchik
86           Author
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NOTES

89        1. maildrop(1)
90           http://www.courier-mta.org/maildrop.html
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92        2. maildirmake(1)
93           http://www.courier-mta.org/maildirmake.html
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95        3. maildropfilter(5)
96           http://www.courier-mta.org/maildropfilter.html
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98        4. deliverquota(8)
99           http://www.courier-mta.org/deliverquota.html
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103Courier Mail Server               11/04/2020                   MAILDIRQUOTA(7)
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