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 |
---|---|---|---|---|---|
841 | Develop | '2014 모바일 개발 트렌드' 발표자료입니다. | hooni | 2014.10.02 | 1130 |
840 | Develop | Aspect Oriented Programming in Objective-C | hooni | 2015.05.18 | 938 |
839 | Develop | DDay Memo 1.9.4 소스코드 | hooni | 2015.10.03 | 0 |
838 | Develop | GCM 사용하기 2 (단말에 GCM 구현하기) | hooni | 2013.07.06 | 23404 |
837 | Develop | GCM 사용하기 3 (JSP로 GCM 푸시 서버 만들기) 4 | hooni | 2013.07.06 | 25415 |
836 | Develop | git 브런치 배우기 (링크) | hooni | 2013.07.09 | 20689 |
835 | Develop | GPL, AGPL, MPL,.. 한눈에 보는 오픈소스SW 라이선스 | hooni | 2014.10.14 | 1253 |
» | Develop | How to Test SMTP AUTH using Telnet | hooni | 2018.04.05 | 1582 |
833 | Develop | JSON, BSON 변환 | hooni | 2013.04.23 | 11863 |
832 | Develop | Laravel 5 Failed opening required bootstrap/../vendor/autoload.php | hooni | 2018.01.24 | 1825 |
831 | Develop | Mac OS 에 Jenkins 설치하기 (Homebrew) 2 | hooni | 2017.03.15 | 8377 |
830 | Develop | macOS에 node, npm 설치하기 (homebrew) | hooni | 2021.11.06 | 1445 |