[Born2beRoot] 보너스 서비스로 sendmail 어때요? ⊂( ・ ̫・)⊃

apt install sendmail sendmail-cf service sendmail status service sendmail start

cp /etc/mail/sendmail.mc /etc/mail/sendmail.mc.original diff /etc/mail/sendmail.mc.original /etc/mail/sendmail.mc m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf cp /etc/mail/sendmail.cf /etc/mail/sendmail.cf.original

service sendmail restart

apt install telnet

telnet localhost 25 # 메일 발송 시작 (telnet 명령어로 25번 포트에 접속 - 메일 서버는 25번 포트를 사용함) helo localhost # helo는 메일 서버에 연결하기 위해 클라이언트의 도메인 이름을 알려주는 명령어 mail from: <현재 접속한 유저 이름>@localhost # 발신자 rcpt to: <이메일 주소> # 수신자 data # 메일 시작 subject: <메일 제목> 메일 본문 . # 메일 본문 종료 quit # 메일 발송 및 종료

# /var/log/mail.log cat /var/log/mail.log | grep <메일 ID>

vi /var/mail/<메일을 전송한 유저ID>

From MAILER-DAEMON Thu Sep 22 19:22:48 2022 Return-Path: <MAILER-DAEMON> Received: from localhost (localhost) by cheseo42 (8.15.2/8.15.2/Debian-14~deb10u1) id 28MAMmCi003042; Thu, 22 Sep 2022 19:22:48 +0900 Date: Thu, 22 Sep 2022 19:22:48 +0900 From: Mail Delivery Subsystem <MAILER-DAEMON> Message-Id: <202209221022.28MAMmCi003042@cheseo42> To: root@cheseo42 MIME-Version: 1.0 Content-Type: multipart/report; report-type=delivery-status; boundary="28MAMmCi003042.1663842168/cheseo42" Subject: Returned mail: see transcript for details Auto-Submitted: auto-generated (failure) This is a MIME-encapsulated message --28MAMmCi003042.1663842168/cheseo42 The original message was received at Thu, 22 Sep 2022 19:22:07 +0900 from localhost [127.0.0.1] ----- The following addresses had permanent fatal errors ----- 메일주소@gmail.com (reason: 550-5.7.26 This message does not pass authentication checks (SPF and DKIM both) ----- Transcript of session follows ----- ... while talking to gmail-smtp-in.l.google.com.: >>> DATA <<< 550-5.7.26 This message does not pass authentication checks (SPF and DKIM both <<< 550-5.7.26 do not pass). SPF check for [cheseo42] does not pass with ip: <<< 550-5.7.26 [121.135.181.35].To best protect our users from spam, the message <<< 550-5.7.26 has been blocked. Please visit <<< 550-5.7.26 https://support.google.com/mail/answer/81126#authentication for more <<< 550 5.7.26 information. me18-20020a17090b17d200b001fb35ed6fdesi6073649pjb.53 - gsmtp 554 5.0.0 Service unavailable --28MAMmCi003042.1663842168/cheseo42 Content-Type: message/delivery-status Reporting-MTA: dns; cheseo42 Received-From-MTA: DNS; localhost Arrival-Date: Thu, 22 Sep 2022 19:22:07 +0900 Final-Recipient: RFC822; 메일주소@gmail.com Action: failed Status: 5.7.26 Remote-MTA: DNS; gmail-smtp-in.l.google.com Diagnostic-Code: SMTP; 550-5.7.26 This message does not pass authentication checks (SPF and DKIM both Last-Attempt-Date: Thu, 22 Sep 2022 19:22:48 +0900 --28MAMmCi003042.1663842168/cheseo42 Content-Type: text/rfc822-headers Return-Path: <root@cheseo42> Received: from localhost (localhost [127.0.0.1]) by cheseo42 (8.15.2/8.15.2/Debian-14~deb10u1) with SMTP id 28MALPCi003039 for 메일주소@gmail.com; Thu, 22 Sep 2022 19:22:07 +0900 Date: Thu, 22 Sep 2022 19:21:25 +0900 From: root <root@cheseo42> Message-Id: <202209221022.28MALPCi003039@cheseo42> subject: hello hello! --28MAMmCi003042.1663842168/cheseo42--