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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1
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4
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通信相手を識別する
■ ドメイン名と IP アドレスを対応づける
IP アドレスで通信できることがわかったところで、メールの送信について
考えてみましょう。送信するにはメールアドレスのドメイン名からそのドメイ
ンを管理しているメールサーバーの IP アドレスへの変換が必要です。つまり、
「abc@shoeisha.co.jp」とい うメー ルア ドレスにメ ール を送信 する には、
「shoeisha.co.jp」というドメイン名に対応するメールサーバーの IP アドレス
が必要です。
実際には、1 つのドメインに複数のサーバーが存在する可能性があるため、
そのサーバーの名前（ホスト名）に対応する IP アドレスが欲しいものです【図
1-22】。
これは、Web ブラウザで Web サイトを閲覧するときに Web サーバーにア
クセスするときも同じで、「https://www.shoeisha.co.jp」という URL にア
クセスするには、「www.shoeisha.co.jp」という Web サーバーの IP アドレ
スが必要です。
このとき、通信相手のサーバーが自宅や会社内にあるのであれば、IP アド
レスを覚えておくこともできるかもしれませんが、世界中からアクセスされる
ようなサーバーであれば、IP アドレスを覚えてもらうのは大変です。サーバー
図 1-22
ホスト名から IP アドレスの取得が必要
abc@shoeisha.co.jpに
メールを送りたい
shoeisha.co.jpの
メールサーバーの ...
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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.