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
No. | Category | Subject | Author | Date | Views |
---|---|---|---|---|---|
1113 | System/OS | 무선 인증 서버.. 김도.. ㅋㅋ | hooni | 2013.04.23 | 17692 |
1112 | System/OS | 무료로 HTTPS 적용하기 (Lets' Encrypt) | hooni | 2017.02.16 | 2385 |
1111 | System/OS | 무료로 HTTPS 적용하기 (Let's Encrypt) | hooni | 2017.10.28 | 1694 |
1110 | Develop | 모터에 대한 pid 제어.. ㅎㅎ | hooni | 2013.04.23 | 18938 |
1109 | Etc | 모바일 프로그래머가 갖추어야 할 필수 역량 | hooni | 2017.02.16 | 1496 |
1108 | System/OS | 맥에서 포트 확인하고 닫기 (mac) | hooni | 2022.03.22 | 1208 |
1107 | System/OS | 맥에서 파일공유 (윈도우,맥) | hooni | 2013.04.25 | 37400 |
1106 | System/OS | 맥북에서 MAC/윈도우 멀티부팅시 시간 설정 | hooni | 2013.04.23 | 29867 |
1105 | System/OS | 맥 OS X 에서 스크린 화면 캡쳐 단축키 (Mac Print Screen) | hooni | 2015.07.21 | 2043 |
1104 | Develop | 링크들 보고 지울 내용 | hooni | 2019.11.21 | 0 |
1103 | Develop | 리팩토링 계획안 | hooni | 2017.05.15 | 873 |
1102 | Develop | 레고 마인드스톰 NXT 수도쿠, 큐브 소스코드.. 20 | hooni | 2013.04.23 | 81585 |