maildirquota(7)
NAME
maildirquota - voluntary Maildir quotas
SYNOPSIS
maildirmake {-q} {10000000S} {./Maildir}
DESCRIPTION
maildrop has a manual quota enforcement implementation that does use
the quota facilities of the host operating system (filesystem-based
quotas). This is an option that is set at configuration time, and may
be disabled.
Using filesystem quotas sometimes leads to problems. After a hard quota
is hit, most commands issued by mail clients fail, including some
commands that poorly-written mail software may not expect to fail, and
therefore be unable to gracefully handle the unexpected failure.
- With manual quotas, the only operations that fail are the ones that
most mail clients expect to fail, when the mailbox is full. However,
filesystem-based quotas cannot be used in some situations, such as
virtual mailboxes. If this experimental feature is enabled, approximate quota enforcement can be implemented by maildrop or deliverquota to whatever extent it´s possible to do so. Quotas are enabled by the -q option to maildirmake. Both maildrop and deliverquota will observe any maildirmake-requested quota. - LIMITATIONS
- This quota mechanism will only work as long as maildrop (or
deliverquota) are the only applications that deliver messages to the
maildir, or as long as other applications implement the same quota
enforcement mechanism. The quota enforcement mechanism is described
separately in the README.maildirquota.html file in the source code distribution. - Quota enforcement will still work, to some extent, if there are other
applications that deliver or modify messages in the maildir. However,
quota enforcement may not kick in immediately when the maildir goes
over quota, in fact the maildir can go over quota by a noticeable
amount. But eventually, as long as maildrop or deliverquota are responsible for delivering the majority of messages, quota enforcement will kick in. Also, other sources of messages may also result in
noticeable performance degradation, because quote recalculation will
become noticeably more expensive. - Also keep in mind that this quota mechanism is generally useless if
mail recipients have direct access to their maildirs. - Finally even under the best conditions this quota enforcement does have
a small chance of a race condition where a maildir will go over quota
by some amount. maildirs are designed for speed, and this quota
implementation was designed to have as little additional overhead as
possible, compared to regular maildirs. To enforce an exact quota you
would have to use some kind of a locking facility, which will impose a drastic performance degradation on the overall maildir performance. A
decision has been made to avoid locking, with the only negative side
effect being a possibility of going over quota in very low probability situations. - A way to minimize the risk of going over quota is to set reasonable
quotas, in relation to maximum message sizes supported by your mail
server. If you set your maildir quota to five gigabytes, for example,
it makes very little sense to configure your mail server to accept
messages up to three gigabytes in size. Your maildir quota should be
chosen so that it makes sense when compared to the maximum message size allowed by your mail server. - FOLDERS
- This quota implementation is compatible with a popular extension to
maildir which defines individual mail folders within a single maildir. However, in order to create a compatible folder, you MUST use the
maildirmake command that comes with maildrop, and you MUST use the -f option to maildirmake, giving the name of the folder. Do not use maildirmake and specify the directory name of the maildir folder. Quota enforcement will not work if you do that.
SEE ALSO
maildrop(1)[1], maildirmake(1)[2], maildropfilter(5)[3],
deliverquota(8)[4].
NOTES
- 1. maildrop(1)
- maildrop.html
- 2. maildirmake(1)
maildirmake.html - 3. maildropfilter(5)
maildropfilter.html - 4. deliverquota(8)
deliverquota.html