このプレスリリースが出たのでDNSを確認してみた。
IN MX 20 mx6.iij4u.or.jp. IN MX 10 mx.iij4u.or.jp.
となっており、MX 10はv4で、DNS ラウンドロビン、 MX 20 は v6 で、DNS ラウンドロビンという状態になっていた。
以前、同一のMXのレコードにAとAAAAを書くと、正しく受信出来ないという問題が、
[janog:08776] デュアルスタックのSMTP
等で報告されていたが、その辺の回避の為だろうか。
$ dig @dns0.iij.ad.jp dd.iij4u.or.jp mx ;; QUESTION SECTION: ;dd.iij4u.or.jp. IN MX ;; ANSWER SECTION: dd.iij4u.or.jp. 900 IN MX 20 mx6.iij4u.or.jp. dd.iij4u.or.jp. 900 IN MX 10 mx.iij4u.or.jp. ;; AUTHORITY SECTION: iij4u.or.jp. 36000 IN NS dns0.iij.ad.jp. iij4u.or.jp. 36000 IN NS dns1.iij.ad.jp. ;; ADDITIONAL SECTION: mx.iij4u.or.jp. 600 IN A 210.138.174.71 mx.iij4u.or.jp. 600 IN A 210.138.174.72 mx.iij4u.or.jp. 600 IN A 210.138.174.69 mx.iij4u.or.jp. 600 IN A 210.138.174.70 mx6.iij4u.or.jp. 600 IN AAAA 2001:240:bb41:8011::1:70 mx6.iij4u.or.jp. 600 IN AAAA 2001:240:bb41:8011::1:71 mx6.iij4u.or.jp. 600 IN AAAA 2001:240:bb41:8011::1:72 mx6.iij4u.or.jp. 600 IN AAAA 2001:240:bb41:8011::1:69 dns0.iij.ad.jp. 86400 IN A 210.138.174.16 dns0.iij.ad.jp. 86400 IN AAAA 2001:240:bb41:8002::1:16 dns1.iij.ad.jp. 86400 IN A 210.138.175.5 dns1.iij.ad.jp. 86400 IN AAAA 2001:240:bb4c:8000::1:5 ;; Query time: 28 msec ;; SERVER: 2001:240:bb41:8002::1:16#53(2001:240:bb41:8002::1:16) ;; WHEN: Wed Jul 28 17:42:11 2010 ;; MSG SIZE rcvd: 380
$ dig @dns0.iij.ad.jp ff.iij4u.or.jp mx ;; QUESTION SECTION: ;ff.iij4u.or.jp. IN MX ;; ANSWER SECTION: ff.iij4u.or.jp. 900 IN MX 10 mx.iij4u.or.jp. ff.iij4u.or.jp. 900 IN MX 20 mx6.iij4u.or.jp.
$ dig @dns0.iij.ad.jp hh.iij4u.or.jp mx ;; QUESTION SECTION: ;hh.iij4u.or.jp. IN MX ;; ANSWER SECTION: hh.iij4u.or.jp. 900 IN MX 10 mx.iij4u.or.jp. hh.iij4u.or.jp. 900 IN MX 20 mx6.iij4u.or.jp.
$ dig @dns0.iij.ad.jp kk.iij4u.or.jp mx ;; QUESTION SECTION: ;kk.iij4u.or.jp. IN MX ;; ANSWER SECTION: kk.iij4u.or.jp. 900 IN MX 20 mx6.iij4u.or.jp. kk.iij4u.or.jp. 900 IN MX 10 mx.iij4u.or.jp.
$ dig @dns0.iij.ad.jp nn.iij4u.or.jp mx ;; QUESTION SECTION: ;nn.iij4u.or.jp. IN MX ;; ANSWER SECTION: nn.iij4u.or.jp. 900 IN MX 10 mx.iij4u.or.jp. nn.iij4u.or.jp. 900 IN MX 20 mx6.iij4u.or.jp.
$ dig @dns0.iij.ad.jp pp.iij4u.or.jp mx ;; QUESTION SECTION: ;pp.iij4u.or.jp. IN MX ;; ANSWER SECTION: pp.iij4u.or.jp. 900 IN MX 10 mx.iij4u.or.jp. pp.iij4u.or.jp. 900 IN MX 20 mx6.iij4u.or.jp.
$ dig @dns0.iij.ad.jp rr.iij4u.or.jp mx ;; QUESTION SECTION: ;rr.iij4u.or.jp. IN MX ;; ANSWER SECTION: rr.iij4u.or.jp. 900 IN MX 20 mx6.iij4u.or.jp. rr.iij4u.or.jp. 900 IN MX 10 mx.iij4u.or.jp.
$ dig @dns0.iij.ad.jp ss.iij4u.or.jp mx ;; QUESTION SECTION: ;ss.iij4u.or.jp. IN MX ;; ANSWER SECTION: ss.iij4u.or.jp. 900 IN MX 10 mx.iij4u.or.jp. ss.iij4u.or.jp. 900 IN MX 20 mx6.iij4u.or.jp.
$ dig @dns0.iij.ad.jp uu.iij4u.or.jp mx ;; QUESTION SECTION: ;uu.iij4u.or.jp. IN MX ;; ANSWER SECTION: uu.iij4u.or.jp. 900 IN MX 10 mi-stg.iij4u.or.jp. uu.iij4u.or.jp. 900 IN MX 20 mi6-stg.iij4u.or.jp. ;; ADDITIONAL SECTION: mi-stg.iij4u.or.jp. 36000 IN A 210.138.174.86 mi6-stg.iij4u.or.jp. 36000 IN AAAA 2001:240:bb41:8011::1:86
$ dig @dns0.iij.ad.jp bc.iij4u.or.jp mx ;; QUESTION SECTION: ;bc.iij4u.or.jp. IN MX ;; ANSWER SECTION: bc.iij4u.or.jp. 900 IN MX 10 mx.iij4u.or.jp. bc.iij4u.or.jp. 900 IN MX 20 mx6.iij4u.or.jp.
$ dig @dns0.iij.ad.jp bk.iij4u.or.jp mx ;; QUESTION SECTION: ;bk.iij4u.or.jp. IN MX ;; ANSWER SECTION: bk.iij4u.or.jp. 900 IN MX 20 mx6.iij4u.or.jp. bk.iij4u.or.jp. 900 IN MX 10 mx.iij4u.or.jp.
$ dig @dns0.iij.ad.jp bp.iij4u.or.jp mx ;; QUESTION SECTION: ;bp.iij4u.or.jp. IN MX ;; ANSWER SECTION: bp.iij4u.or.jp. 900 IN MX 10 mx.iij4u.or.jp. bp.iij4u.or.jp. 900 IN MX 20 mx6.iij4u.or.jp.
$ dig @dns0.iij.ad.jp bu.iij4u.or.jp mx ;; QUESTION SECTION: ;bu.iij4u.or.jp. IN MX ;; ANSWER SECTION: bu.iij4u.or.jp. 900 IN MX 10 mx.iij4u.or.jp. bu.iij4u.or.jp. 900 IN MX 20 mx6.iij4u.or.jp.