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<TD ALIGN="center" VALIGN="middle"><IMG ALT="Binc IMAP logo" SRC="b-button64.png" BORDER="0"></TD>
<TD ALIGN="center" VALIGN="middle">Binc IMAP - IMAPdir</TD>
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<A HREF="http://www.gnu.org/licenses/gpl.html">GNU General Public License</A><BR>
Andreas Aardal Hanssen <andreas@hanssen.name>
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<BLOCKQUOTE>
<P>This document describes the generic mail folder structure
<B>IMAPdir</B>.</P>
<P>The goal of the work behind this specification is to provide the
community with an unambiguous representation of a mailbox hierarchy
where a mailbox name has a one-to-one match against a file system
representation. The hierarchy and naming style is inspired by the
IMAP4 protocol.</P>
<P>Rather than being a completely new mailbox format, this specification
sets conventions on how to represent a mailbox hierarchy on a file
system, using existing mailbox formats. <B>IMAPdir</B> is not bound to
any protocol.</P>
<P><B>IMAPdir</B> works with any mailbox format where one mailbox can
be identified by a file, a directory or a symbolic link. One entry in
an <B>IMAPdir</B> folder is a candidate for a mailbox. If the
<B>IMAPdir</B> client can not identify a directory entry as a
selectable mailbox, then the client must either skip the entry or
mark it as invalid (in IMAP, marked as \NoSelect).</P>
<UL>
<LI>There is no limitation to the type of file system or the number of
file systems represented inside an <B>IMAPdir</B>.</LI>
<LI>There are no reserved ordinary folder
names such as "Sent", "Draft" or "Trash".</LI>
<LI>Clients of the mailboxes inside an <B>IMAPdir</B>
folder <I>must</I> follow the respective format and protocol conventions
strictly.</LI>
</UL>
<P>The format of a mailbox representation in <B>IMAPdir</B> is a
sequence of one or more US-ASCII characters (32-126), encoded using
the following rules:</P>
<UL>
<LI>A dot '.' character represents a soft hierarchy delimiter with two exceptions:
<UL>
<LI>A leading dot represents the dot itself.</LI>
<LI>A dot '.' preceded by a backslash '\' represents the dot '.' itself.</LI>
</UL>
</LI>
<LI>A backslash '\' preceded by a backslash '\' represents the backslash '\' itself. For all other cases than before a dot '.' or a backslash '\', a stray backslash '\' character is considered an error.</LI>
<LI>A backslash '\' as the first character of an entry is considered an error.</LI>
<LI>All other characters represent themselves.</LI>
</UL>
Note that the protocol used to fetch the mailbox using the
structuring <B>IMAPdir</B> convention may restrict the character set
allowed. The clients <I>must</I> in those cases translate the mailbox
names to a selectable format.
<P>As with <A
HREF="http://www.inter7.com/courierimap/README.maildirquota.html">Maildir++</A>,
submailboxes can not be represented in a recursive fashion in the file
system. The mailbox' representation name will contain the soft
hierarchy delimiter character dot '.', and all mailboxes must reside
in the same root level directory.</P>
<P>The following example shows the typical content of an
<B>IMAPdir</B> stored under the directory <B>mail/</B>. The <B>file
system</B> column displays the contents as viewed by the UNIX command
'ls -al -F'.</P>
<TABLE ALIGN="center" CELLSPACING="5" CELLPADDING="5">
<TR>
<TH BGCOLOR="#555555">File system
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<TH BGCOLOR="#555555">IMAP
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<TH BGCOLOR="#555555">Description
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<PRE>
mail/INBOX -> /var/mail/paul
mail/INBOX.old/ -> ../Maildir/
mail/INBOX.outbox/
mail/work
mail/3rd\. of July
mail/Sent.2003.Jan/
mail/Sent.2003.Feb/
mail/Sent.2003.Mar/
mail/.foo
</PRE>
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<PRE>
"INBOX"
"INBOX/old"
"INBOX/outbox"
"work"
"3rd. of July"
"Sent/2003/Jan"
"Sent/2003/Feb"
"Sent/2003/Mar"
".foo"
</PRE>
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<TD BGCOLOR="#555555">
<PRE>
Symbolic link to mbox
Symbolic link to Maildir
Maildir
mbox
mbox
Maildir
Maildir
Maildir
mbox
</PRE>
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<P>In other multi level mailbox formats, <B>INBOX</B> is treated as a
special case.</P>
<BLOCKQUOTE>
<P><U><B>Maildir++</B></U></P>
<UL>
<LI><A
HREF="http://www.inter7.com/courierimap/README.maildirquota.html">Maildir++</A>
defines the mail directory itself as
<B>INBOX</B>. Any subdirectories inside starting with a single dot
'.', and containing the file <B>maildirfolder</B> are interpreted as
a <A
HREF="http://www.inter7.com/courierimap/README.maildirquota.html">Maildir++</A>
submailbox.
<LI><P>A <A HREF="http://cr.yp.to/proto/maildir.html">Maildir</A> is by
Dan J. Bernstein's definition identified by a directory that
contains the subdirectories <B>cur</B>,
<B>new</B> and <B>tmp</B> and nothing else.</LI>
<LI>The <A
HREF="http://www.inter7.com/courierimap/README.maildirquota.html">Maildir++</A>
definition follows naturally from <A
HREF="http://www.inter7.com/courierimap/README.maildirquota.html">Maildir++</A>
being an extension to Dan J. Bernstein's <A
HREF="http://cr.yp.to/proto/maildir.html">Maildir</A>
format. However, although the directory ~/Maildir/ itself is a
standard representation of INBOX for <A
HREF="http://cr.yp.to/proto/maildir.html">Maildir</A> clients, it is
not standard for other mailbox formats. With <A
HREF="http://www.inter7.com/courierimap/README.maildirquota.html">Maildir++</A>,
your mailboxes and INBOX in particular must be a <A
HREF="http://cr.yp.to/proto/maildir.html">Maildir</A>.
</UL>
<P><U><B>mbox</B></U></P>
<UL>
<LI>When using the <B>mbox</B> storage format, the user's INBOX is typically
stored at /var/spool/mail/<username>.</LI>
<LI>Using this format, the mail depository client must both have the
path to the user's INBOX <I>and</I> the path to the user's local
mailbox depository, typically <B>mail/</B>.</LI>
</UL>
</BLOCKQUOTE>
<P>Note that although <B>IMAPdir</B> has no restrictions with regards
to mailbox names, the protocol that uses <B>IMAPdir</B> might. For
example, IMAP servers will require the mailbox <B>INBOX</B> to be
present.</P>
<HR>
<P>Last updated on <B>2003-03-20</B>.</P>
<P>Please direct comments to <B>IMAPdir</B> or this document to the
<A HREF="/#mailinglist">Binc IMAP mailing list</A>. Remember to <I>search the archives</I>
first.</P>
</BLOCKQUOTE>
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