1MAILDIRQUOTA(7) Double Precision, Inc. MAILDIRQUOTA(7)
2
6 maildirquota - voluntary Maildir quotas
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9 maildirmake {-q} {10000000S} {./Maildir}
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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.
16 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.
21 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.
30 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 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.
48 Also keep in mind that this quota mechanism is generally useless if
50 mail recipients have direct access to their maildirs.
51 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.
62 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.
70 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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81 maildrop(1)[1], maildirmake(1)[2], maildropfilter(5)[3],
82 deliverquota(8)[4].
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85 Sam Varshavchik
86 Author
87
89 1. maildrop(1)
90 http://www.courier-mta.org/maildrop.html
91 2. maildirmake(1)
93 http://www.courier-mta.org/maildirmake.html
94 3. maildropfilter(5)
96 http://www.courier-mta.org/maildropfilter.html
97 4. deliverquota(8)
99 http://www.courier-mta.org/deliverquota.html
100Courier Mail Server 11/04/2020 MAILDIRQUOTA(7)