How to manually test SMTP Authentication

Written by Shai Ben-Naphtali Saturday, 19 December 2009

Related documents:

1. Base64 encoder
2. How to Use Telnet to Test SMTP Communication
3. GRC’s Ultra High Security Password Generator
4. The PC Tools Password Generator

Sometimes, you find yourself not knowing if you have the right credentials to do SMTP Authentication. This might be because your mail client that you are so used to, is just a GUI (Graphic User Interface) for doing things the easy way. In this blog, I’ll show you (a bit of) what your mail client does in order to authenticate and send an email via an SMTP server/service.

This guide, with just using telnet, will allow you to test if you can even do SMTP on port 25 from within your LAN/Organization or behind your Anti-Virus/Firewall.

First, you need to get your username/email address and your password, encoded into a base64 data encoding scheme [2] or use perl (as I’ll show below).

First Option:

• Use the web based encoder [2] to encode your username/email address and your password.
  • 
    The outcome of the above will produce: c2hhaUBzaGFpLWFydml4ZS5jb20=
  • 
    The outcome of the above will produce: bjw1JWptPm5+OWtjVjdpRi9IIl5HcEhnaHMwNX53eE1KPCYsSWZjOTN2Ln1fMmJRPlJlUHFecXI9U3MpLClm

Second Option:

• shai@ubuntu:~$ perl -MMIME::Base64 -e ‘print encode_base64(“shai\@shai-arvixe.com”);’
  c2hhaUBzaGFpLWFydml4ZS5jb20=
  (Note: Notice how I had to escape the @ sign with a backslash)
• shai@ubuntu:~$ perl -MMIME::Base64 -e ‘print encode_base64(“n<5%jm>n~9kcV7iF/H\“^GpHghs05~wxMJ<&,Ifc93v.}_2bQ>RePq^qr=Ss),)f”);’
  bjw1JWptPm5+OWtjVjdpRi9IIl5HcEhnaHMwNX53eE1KPCYsSWZjOTN2Ln1fMmJRPlJlUHFecXI9U3MpLClm
  (Note: Notice how I had to escape the “ sign with a backslash)

Now you can use telnet on your Windows/Linux box to test the SMTP Authentication:
(In Orange is text I typed)

• shai@ubuntu:~$ telnet test.arvixe.com 25
  Trying 192.168.1.200…
  Connected to test.arvixe.com.
  Escape character is ‘^]’.
  220-test.arvixe.com ESMTP Exim
  220-We do not authorize the use of this system to transport unsolicited,
  220 and/or bulk e-mail.
  EHLO
  250-test.arvixe.com Hello l192-168-1-199.cable.internal.net [192.168.1.199]
  250-SIZE 52428800
  250-PIPELINING
  250-AUTH PLAIN LOGIN
  250-STARTTLS
  250 HELP
  AUTH LOGIN
  334 VXNlcm5hbWU6
  c2hhaUBzaGFpLWFydml4ZS5jb20=
  334 UGFzc3dvcmQ6
  bjw1JWptPm5+OWtjVjdpRi9IIl5HcEhnaHMwNX53eE1KPCYsSWZjOTN2Ln1fMmJRPlJlUHFecXI9U3MpLClm
  235 Authentication succeeded
  MAIL FROM: [email protected]
  250 OK
  RCPT TO: [email protected]
  250 Accepted
  DATA
  354 Enter message, ending with “.” on a line by itself
  From: Shai’s blog <[email protected]>
  Subject: testing 0940
  This is another test.
  —
  Shai
  .
  250 OK id=1NLtun-0005EK-6i
• Well, what do you know, it arrived