-“<span class="quote">Reply-To</span>” field which points back to the mailing list address rather
-than the author of the message. This can create problems when trying
-to reply directly to the author in private, since most mail clients
-will automatically reply to the address given in the “<span class="quote">Reply-To</span>”
-field. Mutt uses the <a class="link" href="#reply-to" title="3.214. reply_to">$reply_to</a>
-variable to help decide which address to use. If set to <span class="emphasis"><em>ask-yes</em></span> or
-<span class="emphasis"><em>ask-no</em></span>, you will be
-prompted as to whether or not you would like to use the address given in
-the “<span class="quote">Reply-To</span>” field, or reply directly to the address given in the
-“<span class="quote">From</span>” field. When set to <span class="emphasis"><em>yes</em></span>, the “<span class="quote">Reply-To</span>” field will be used when
-present.
-</p><p>
-The “<span class="quote">X-Label:</span>” header field can be used to further identify mailing
-lists or list subject matter (or just to annotate messages
-individually). The <a class="link" href="#index-format" title="3.114. index_format">$index_format</a> variable's “<span class="quote">%y</span>” and
-“<span class="quote">%Y</span>” expandos can be used to expand “<span class="quote">X-Label:</span>” fields in the
-index, and Mutt's pattern-matcher can match regular expressions to
-“<span class="quote">X-Label:</span>” fields with the “<span class="quote">˜y</span>” selector. “<span class="quote">X-Label:</span>” is not a
-standard message header field, but it can easily be inserted by procmail
-and other mail filtering agents.
-</p><p>
-Lastly, Mutt has the ability to <a class="link" href="#sort" title="3.263. sort">sort</a> the mailbox into
-<a class="link" href="#threads" title="5.3. Threaded Mode">threads</a>. A thread is a group of messages which all relate to the same
-subject. This is usually organized into a tree-like structure where a
-message and all of its replies are represented graphically. If you've ever
-used a threaded news client, this is the same concept. It makes dealing
-with large volume mailing lists easier because you can easily delete
-uninteresting threads and quickly find topics of value.
-</p></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="handling-folders"></a>9. Handling multiple folders</h2></div></div></div><p>
-Mutt supports setups with multiple folders, allowing all of them to
-be monitored for new mail (see <a class="xref" href="#mailboxes" title="14. Monitoring Incoming Mail">Section 14, “Monitoring Incoming Mail”</a> for details).
-</p><p>
-When in the index menu and being idle (also see
-<a class="link" href="#timeout" title="3.291. timeout">$timeout</a>), Mutt periodically checks
-for new mail in all folders which have been configured via the
+<span class="quote">“<span class="quote">Reply-To</span>”</span> field which points back to the mailing list
+address rather than the author of the message. This can create problems
+when trying to reply directly to the author in private, since most mail
+clients will automatically reply to the address given in the
+<span class="quote">“<span class="quote">Reply-To</span>”</span> field. Mutt uses the <a class="link" href="#reply-to" title="3.215. reply_to">$reply_to</a> variable to help decide which
+address to use. If set to <span class="emphasis"><em>ask-yes</em></span> or
+<span class="emphasis"><em>ask-no</em></span>, you will be prompted as to whether or not
+you would like to use the address given in the <span class="quote">“<span class="quote">Reply-To</span>”</span>
+field, or reply directly to the address given in the <span class="quote">“<span class="quote">From</span>”</span>
+field. When set to <span class="emphasis"><em>yes</em></span>, the
+<span class="quote">“<span class="quote">Reply-To</span>”</span> field will be used when present.
+</p><p>
+The <span class="quote">“<span class="quote">X-Label:</span>”</span> header field can be used to further identify
+mailing lists or list subject matter (or just to annotate messages
+individually). The <a class="link" href="#index-format" title="3.114. index_format">$index_format</a>
+variable's <span class="quote">“<span class="quote">%y</span>”</span> and <span class="quote">“<span class="quote">%Y</span>”</span> expandos can be used
+to expand <span class="quote">“<span class="quote">X-Label:</span>”</span> fields in the index, and Mutt's
+pattern-matcher can match regular expressions to <span class="quote">“<span class="quote">X-Label:</span>”</span>
+fields with the <span class="quote">“<span class="quote">~y</span>”</span> selector. <span class="quote">“<span class="quote">X-Label:</span>”</span> is
+not a standard message header field, but it can easily be inserted by
+procmail and other mail filtering agents.
+</p><p>
+Lastly, Mutt has the ability to <a class="link" href="#sort" title="3.264. sort">sort</a> the
+mailbox into <a class="link" href="#threads" title="5.3. Threaded Mode">threads</a>. A thread is a
+group of messages which all relate to the same subject. This is usually
+organized into a tree-like structure where a message and all of its
+replies are represented graphically. If you've ever used a threaded
+news client, this is the same concept. It makes dealing with large
+volume mailing lists easier because you can easily delete uninteresting
+threads and quickly find topics of value.
+</p></div><div class="sect1" title="10. New Mail Detection"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="new-mail"></a>10. New Mail Detection</h2></div></div></div><p>
+Mutt supports setups with multiple folders, allowing all of them to be
+monitored for new mail (see <a class="xref" href="#mailboxes" title="14. Monitoring Incoming Mail">Section 14, “Monitoring Incoming Mail”</a> for details).
+</p><div class="sect2" title="10.1. How New Mail Detection Works"><div class="titlepage"><div><div><h3 class="title"><a id="new-mail-formats"></a>10.1. How New Mail Detection Works</h3></div></div></div><p>
+For Mbox and Mmdf folders, new mail is detected by comparing access
+and/or modification times of files: Mutt assumes a folder has new mail
+if it wasn't accessed after it was last modified. Utilities like
+<code class="literal">biff</code> or <code class="literal">frm</code> or any other program
+which accesses the mailbox might cause Mutt to never detect new mail for
+that mailbox if they do not properly reset the access time. Other
+possible causes of Mutt not detecting new mail in these folders are
+backup tools (updating access times) or filesystems mounted without
+access time update support (for Linux systems, see the
+<code class="literal">relatime</code> option).
+</p><div class="note" title="Note"><h3 class="title">Note</h3><p>
+Contrary to older Mutt releases, it now maintains the new mail status of
+a folder by properly resetting the access time if the folder contains at
+least one message which is neither read, nor deleted, nor marked as old.
+</p></div><p>
+In cases where new mail detection for Mbox or Mmdf folders appears to be
+unreliable, the <a class="link" href="#check-mbox-size" title="3.26. check_mbox_size">$check_mbox_size</a>
+option can be used to make Mutt track and consult file sizes for new
+mail detection instead which won't work for size-neutral changes.
+</p><p>
+New mail for Maildir is assumed if there is one message in the
+<code class="literal">new/</code> subdirectory which is not marked deleted (see
+<a class="link" href="#maildir-trash" title="3.123. maildir_trash">$maildir_trash</a>). For MH folders, a
+mailbox is considered having new mail if there's at least one message in
+the <span class="quote">“<span class="quote">unseen</span>”</span> sequence as specified by <a class="link" href="#mh-seq-unseen" title="3.140. mh_seq_unseen">$mh_seq_unseen</a>.
+</p><p>
+Mutt does not poll POP3 folders for new mail, it only periodically
+checks the currently opened folder (if it's a POP3 folder).
+</p><p>
+For IMAP, by default Mutt uses recent message counts provided by the
+server to detect new mail. If the <a class="link" href="#imap-idle" title="3.100. imap_idle">$imap_idle</a> option is set, it'll use the IMAP
+IDLE extension if advertised by the server.
+</p></div><div class="sect2" title="10.2. Polling For New Mail"><div class="titlepage"><div><div><h3 class="title"><a id="new-mail-polling"></a>10.2. Polling For New Mail</h3></div></div></div><p>
+When in the index menu and being idle (also see <a class="link" href="#timeout" title="3.292. timeout">$timeout</a>), Mutt periodically checks for new
+mail in all folders which have been configured via the
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