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+Mbox Locking
+============
+
+The only standard way to lock an mbox is using a method called "dotlock". This
+means that a file named '<mailbox-name>.lock' is created in the same directory
+as the mailbox being locked. This works pretty well when the mbox is locked for
+writing, but for reading it's very inefficient. That's why other locking
+methods have been used.
+
+*It's important that all software that's reading or writing to mboxes use the
+same locking settings.* If they use different methods, they might read/write to
+an mbox while another process is modifying it, and see corrupted mails. If they
+use the same methods but in a different order, they can both end up in a
+deadlock.
+
+If you want to know more details about locking, see <the mbox format page>
+[MailboxFormat.mbox.txt].
+
+For Dovecot you can configure locking using the 'mbox_read_locks' and
+'mbox_write_locks' settings. The defaults are:
+
+---%<-------------------------------------------------------------------------
+mbox_read_locks = fcntl
+mbox_write_locks = dotlock fcntl
+---%<-------------------------------------------------------------------------
+
+Here's a list of how to find out the locking settings for other software:
+
+Procmail
+--------
+
+---%<-------------------------------------------------------------------------
+# procmail -v 2>&1|grep Locking
+Locking strategies:     dotlocking, fcntl()
+---%<-------------------------------------------------------------------------
+
+Postfix
+-------
+
+Postfix has two different ways to deliver to mboxes. One is the "mailbox"
+transport and another one is the "virtual" transport.
+
+---%<-------------------------------------------------------------------------
+# postconf mailbox_delivery_lock
+mailbox_delivery_lock = fcntl, dotlock
+# postconf virtual_mailbox_lock
+virtual_mailbox_lock = fcntl
+---%<-------------------------------------------------------------------------
+
+In the above case, if you used the "mailbox" transport, you'd have to change
+Dovecot's configuration to 'mbox_write_locks = fcntl dotlock' or vice versa for
+Postfix.
+
+If you used the "virtual" transport, it doesn't really matter if the "dotlock"
+is missing, since the "fcntl" is common with Dovecot and Postfix.
+
+mutt
+----
+
+---%<-------------------------------------------------------------------------
+mutt -v|grep -i lock
+---%<-------------------------------------------------------------------------
+
+Debian
+------
+
+Debian's policy specifies that all software should use "fcntl and then dotlock"
+locking, but this probably applies only to most commonly used software.
+
+(This file was created from the wiki on 2019-06-19 12:42)