23. $ dig mx hiroba.org ;; QUESTION SECTION: ;hiroba.org. IN MX ;; ANSWER SECTION: hiroba.org. 86400 IN MX 5 alt1.aspmx.l.google.com. hiroba.org. 86400 IN MX 5 alt2.aspmx.l.google.com. hiroba.org. 86400 IN MX 10 aspmx2.googlemail.com. hiroba.org. 86400 IN MX 10 aspmx3.googlemail.com. hiroba.org. 86400 IN MX 10 aspmx4.googlemail.com. hiroba.org. 86400 IN MX 10 aspmx5.googlemail.com. hiroba.org. 86400 IN MX 1 aspmx.l.google.com. ;; AUTHORITY SECTION: hiroba.org. 170129 IN NS ns-165.awsdns-20.com. hiroba.org. 170129 IN NS ns-1624.awsdns-11.co.uk. hiroba.org. 170129 IN NS ns-1347.awsdns-40.org. hiroba.org. 170129 IN NS ns-1003.awsdns-61.net. ;; ADDITIONAL SECTION: aspmx.l.google.com. 185 IN A 74.125.127.27 alt1.aspmx.l.google.com. 187 IN A 74.125.45.27 alt2.aspmx.l.google.com. 197 IN A 74.125.93.27 aspmx2.googlemail.com. 2212 IN A 74.125.43.27 aspmx3.googlemail.com. 2213 IN A 74.125.127.27 aspmx4.googlemail.com. 2945 IN A 209.85.229.27 aspmx5.googlemail.com. 1888 IN A 74.125.157.27 ns-165.awsdns-20.com. 44352 IN A 205.251.192.165 ns-1003.awsdns-61.net. 44352 IN A 205.251.195.235 ns-1347.awsdns-40.org. 162645 IN A 205.251.197.67
24. DNSを使った送信先決定 DNS root server DNS cache server MTA 2 1,5 .com SOA 3 Example.comのMXレコード? Example.comのMXレコード?->.comに聞け Example.comのMXレコード?->.example.comに聞け Example.comのMXレコード?->10 mail.example.comだよ Mail.example.comのAレコード?.... .example.comSOA 4
25. SMTP HELO sender.example.com 250 OK MAIL FROM: user@example.com 250 OK example.jp Sender.example.com RCPT TO: user1@example.jp 250 OK MTA MUA DATA 354 Start ヘッダ,本文.. <CRLF>.<CRLF> 250 OK QUIT 250 OK
27. メーリングリスト配送の場合 HELO sender.example.com 250 OK MAIL FROM: user@example.com RCPT TO: user1@example.jp 250 OK 配送サーバ MLプログラム 250 OK RCPT TO: user2@example.jp 250 OK 参加者分くりかえし DATA 354 Start ヘッダ,本文.. <CRLF>.<CRLF> 250 OK QUIT 250 OK