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 |
---|---|---|---|---|---|
189 | Develop | [ios] Swift 4 Singleton inheritance | hooni | 2018.10.31 | 1695 |
188 | System/OS |
[mac] OS X 요세미티 사용자가 많이 겪는 버그와 몇몇 불편사항
![]() |
hooni | 2015.01.04 | 1690 |
187 | Develop | [ios] 스크린 캡쳐 (전원버튼 + 홈버튼) 호출 알아내기 | hooni | 2014.11.19 | 1660 |
186 | Develop |
[ios] binary를 C코드로 변환
![]() |
hooni | 2015.01.03 | 1652 |
185 | System/OS | OpenSSL로 ROOT CA 생성 및 SSL 인증서 발급하기 | hooni | 2017.10.28 | 1646 |
184 | Etc |
IT감사 기법 시험
![]() |
hooni | 2017.06.14 | 1635 |
183 | Database |
[mysql] MacOS에 MySQL 설치, 설정, 암호 재설정
![]() |
hooni | 2017.12.15 | 1630 |
182 | Develop | [android] 레이아웃 사이즈 변경 (동적; programmatically) | hooni | 2016.11.07 | 1625 |
181 | System/OS | [linux] wget 명령 사용 예제 | hooni | 2020.05.26 | 1622 |
180 | Develop |
[swift] popToRoot 모달뷰, 네비게이션컨트롤러 한꺼번에 닫기
![]() |
hooni | 2021.01.29 | 1608 |
» | Develop | How to Test SMTP AUTH using Telnet | hooni | 2018.04.05 | 1595 |
178 | Develop | What is difference between Get, Post, Put and Delete? | hooni | 2018.02.28 | 1577 |