How to Test SMTP AUTH using Telnet
Below are instructions on how to test SMTP AUTH against a mail server using Telnet and entering the commands by hand.
The first thing you need to do is get a base64 encoding of your username and password. There are a couple ways to do this, the example below uses Perl:
perl -MMIME::Base64 -e 'print encode_base64("username");' perl -MMIME::Base64 -e 'print encode_base64("password");'
What will be returned from each command is a base64 encoding of the username and password; save these as you will need them later. Now connect to the mail server using Telnet:
telnet mailserver.com 25
Greet the mail server:
EHLO mailserver.com
Tell the server you want to authenticate with it:
AUTH LOGIN
The server should have returned 334 VXNlcm5hbWU6;
this is a base64 encoded string asking you for your username, paste the base64 encoded username you created earlier, example:
dXNlcm5hbWUuY29t
Now the server should have returned 334 UGFzc3dvcmQ6;
. Again this is a base64 encoded string now asking for your password, paste the base64 encoded password you created, example:
bXlwYXNzd29yZA==
Now you should have received a message telling you that you successfully authenticated. If it failed your user/pass may have been wrong or your mailserver is broken.
Below is a log of a real successful SMTP AUTH connection over Telnet:
user@localhost [~]# telnet exampledomain.com 25 Trying 1.1.1.1... Connected to exampledomain.com (1.1.1.1). Escape character is '^]'. 220-server1.exampledomain.com ESMTP Exim 4.66 #1 Wed, 09 May 2007 23:55:12 +0200 220-We do not authorize the use of this system to transport unsolicited, 220 and/or bulk e-mail. EHLO exampledomain.com 250-server1.exampledomain.com Hello [1.1.1.2] 250-SIZE 52428800 250-PIPELINING 250-AUTH PLAIN LOGIN 250-STARTTLS 250 HELP AUTH LOGIN 334 VXNlcm5hbWU6 dXNlcm5hbWUuY29t 334 UGFzc3dvcmQ6 bXlwYXNzd29yZA== 235 Authentication succeeded
번호 | 분류 | 제목 | 글쓴이 | 날짜 | 조회 수 |
---|---|---|---|---|---|
21 | System/OS | [펌] 마이크로서비스, 모노리포, SRE, ... 덮어놓고 구글 따라하면 안 되는 기술들 | hooni | 2020.10.15 | 1085 |
20 | Develop | [ubuntu] 우분투 18.04에 PHP5 설치하기 | hooni | 2020.11.14 | 1072 |
19 | Develop | [kotlin] 코틀린 안드로이드 앱 버전/빌드 정보 | hooni | 2020.12.15 | 968 |
18 | Develop | [swift] NotificationCenter 간단 예제 | hooni | 2021.01.27 | 8312 |
17 | Develop | [swift] popToRoot 모달뷰, 네비게이션컨트롤러 한꺼번에 닫기 | hooni | 2021.01.29 | 1538 |
16 | Develop | [js] show/hide 이벤트 감시 (Observing show/hide event) | hooni | 2021.02.03 | 2739 |
15 | Develop | [vim] vim 명령으로  문자 제거하기 (remove 65279 bomb) | hooni | 2021.02.03 | 1358 |
14 | Develop | [swift] 실행시간 측정하기 | hooni | 2021.09.14 | 814 |
13 | Develop | [iOS] Xcode 불필요한 캐시 삭제하기 | hooni | 2021.10.12 | 1939 |
12 | Develop | [iOS] 시뮬레이터에 푸시 알림을 보내는 방법 | hooni | 2021.10.13 | 1971 |
11 | Develop | macOS에 node, npm 설치하기 (homebrew) | hooni | 2021.11.06 | 1433 |
10 | System/OS | [apache2] Redirect HTTP to HTTPS | hooni | 2022.02.03 | 825 |