February 2024
Beginner to intermediate
304 pages
9h 13m
Japanese
Content preview from 実務で使える メール技術の教科書 基本のしくみからプロトコル・サーバー構築・送信ドメイン認証・添付ファイル・暗号化・セキュリティ対策まで
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3
4
DNSを設定する
つまり、最初に「mx1.example.jp」というメールサーバーに配信を試み、
接続できなかった場合に「mx2.example.jp」に配信を試みることを意味して
います。優先度が同じレコードが複数記述されていた場合は、ランダムな順序
で配信を試みます。前ページの指定ではさらに、それぞれのサーバーの IP ア
ドレスを A レコードで記述しています。
実際に、MX レコードを設定してみましょう。まずは DNS サーバーの設定
画面にログインします。VPS やレンタルサーバーでは、管理者画面から DNS
の設定画面が用意されています【図 3-5】。
このような画面で、メールサーバーのホスト名に対し、種別の欄で「MX」
を選び、内容の欄にホスト名を入力し、TTL や優先度を設定すれば完了です。
あとはここで設定したドメインで、作成したユーザー名にメールを送信すれば
届くはずです。
■ DNS の設定を確認する
DNS 情報が正しく設定できたことを確認するために、一般的にはコマンド
ラインツールで問い合わせる方法が使われます。Windows や macOS では
「nslookup」というコマンドが標準で用意されています。
図 3-5
DNS の設定画面の例
131
D
N
S
125-154̲mail̲NSM̲F2.indd131125-154̲mail̲NSM̲F2.indd131 2024/01/259:532024/01/259:53
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.