bpo-38486: Fix dead qmail links in the mailbox docs (GH-22239)

Doc/library/mailbox.rst

@@ -426,17 +426,14 @@ Supported mailbox formats are Maildir, mbox, MH, Babyl, and MMDF.
 
 .. seealso::
 
-   `maildir man page from qmail <http://www.qmail.org/man/man5/maildir.html>`_
-      The original specification of the format.
+   `maildir man page from Courier <http://www.courier-mta.org/maildir.html>`_
+      A specification of the format. Describes a common extension for
+      supporting folders.
 
    `Using maildir format <https://cr.yp.to/proto/maildir.html>`_
       Notes on Maildir by its inventor. Includes an updated name-creation scheme and
       details on "info" semantics.
 
-   `maildir man page from Courier <http://www.courier-mta.org/maildir.html>`_
-      Another specification of the format. Describes a common extension for supporting
-      folders.
-
 
 .. _mailbox-mbox:
 
@@ -485,11 +482,8 @@ Supported mailbox formats are Maildir, mbox, MH, Babyl, and MMDF.
 
 .. seealso::
 
-   `mbox man page from qmail <http://www.qmail.org/man/man5/mbox.html>`_
-      A specification of the format and its variations.
-
    `mbox man page from tin <http://www.tin.org/bin/man.cgi?section=5&topic=mbox>`_
-      Another specification of the format, with details on locking.
+      A specification of the format, with details on locking.
 
    `Configuring Netscape Mail on Unix: Why The Content-Length Format is Bad <https://www.jwz.org/doc/content-length.html>`_
       An argument for using the original mbox format rather than a variation.