All but the oldest of those mails will be modified (if needed) to
reflect that the oldest mail is the parent of all other mails
+Given 4 files A, B, C, and D like
+
+ File Message-Id Date
+ A 123AC_12 2016-06-01 12:13:14
+ B aFFde2993 2016-06-01 13:14:15
+ C 0000_1234 2016-06-02 10:18:04
+ D foo_bar_12 2016-06-03 04:00:00
+
+The new tree will be like
+
+ A 123AC_12 2016-06-01 12:13:14
+ +- B aFFde2993 2016-06-01 13:14:15
+ +- C 0000_1234 2016-06-02 10:18:04
+ +- D foo_bar_12 2016-06-03 04:00:00
+
+and not
+
+ A 123AC_12 2016-06-01 12:13:14
+ +- B aFFde2993 2016-06-01 13:14:15
+ +- C 0000_1234 2016-06-02 10:18:04
+ +- D foo_bar_12 2016-06-03 04:00:00
+
=head1 SEE ALSO
L<Date::Parse>, L<Claws Mail|http://www.claws-mail.org>