-The prefix can instead specify the format of the output: C<maildir>,
-C<mboxrd>, C<mboxcl2>, C<mboxcl>, C<mboxo>, C<json>, C<jsonl>, or
-C<concatjson>. When a format isn't specified, it's chosen based on
-the destination. C<json> is used for the default destination
-(stdout), and C<maildir> is used for an existing directory or
-non-existing path.
+A prefix can specify the format of the output: C<maildir>,
+C<mboxrd>, C<mboxcl2>, C<mboxcl>, C<mboxo>. For a description of
+mail formats, see L<lei-mail-formats(5)>.
+
+C<maildir> is the default for an existing directory or non-existing path.
+
+Default: C<-> (stdout)