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 |
---|---|---|---|---|---|
1113 | Develop | [c] 파일명 또는 특정 패턴을 적용 | hooni | 2016.08.03 | 752 |
1112 | Develop | [Android Error] The number of method references in a .dex file cannot exceed 64K | hooni | 2016.11.10 | 756 |
1111 | Develop | [linux] CentOS Apache 웹서버에 HTTPS 적용 | hooni | 2015.10.23 | 786 |
1110 | System/OS | [macos] How to Fix ‘You Shut Down Your Computer Because of a Problem’ | hooni | 2022.06.01 | 791 |
1109 | Develop | [io] Apple Watch, Today Extension 앱ID 설정 | hooni | 2016.04.20 | 796 |
1108 | Algorithm | OCB5 Injection 앗싸뵹! ㅋㅋ | hooni | 2014.07.01 | 800 |
1107 | System/OS | [linux] The Ultimate Wget Download Guide With 15 Awesome Examples | hooni | 2020.05.26 | 802 |
1106 | Develop | [js] e.stopPropagation() VS e.preventDefault () | hooni | 2015.04.14 | 808 |
1105 | Develop | [c] 기막힌 정렬 코드 ㅋㄷ | hooni | 2015.10.13 | 810 |
1104 | Develop | [android] 초간단 얼럿 (AlertDialog) | hooni | 2016.10.21 | 811 |
1103 | Etc | 사이버보안실무 수업 메모 | hooni | 2017.03.30 | 811 |
1102 | Database | [mysql] MySQL 백업 및 복구 | hooni | 2019.11.22 | 821 |