Test SMTP authentication

When you have a problem connecting to your ISP's SMTP server from a device such as a Copy machine , or scanner, diagnosis is often difficicult. The same account may connect using an email client. You need an alternate method to view the responses from the SMTP server in real time. Telnet provides a solution. Using telnet you can authenticate the username & password & send an email once authenticated.

First thing to note is that , the request for authenticaton & your response are conducted using base64 encoding. You can use an online source to perform this conversion for you. This is one such resource. http://www.motobit.com/util/base64-decoder-encoder.asp

Using this resource I converted the following to base64 encoding

username/email address sender@sender.com c2VuZGVyQHNlbmRlci5jb20=
password 123abc MTIzYWJj

1. Telnet client needs to be installed , it is no longer installed by default.
2. CASE is very important

Open a telnet session to the mail server , you need to specify the SMTP port , even if it is at the default port of 25.

C:>telnet smtp.domainname.com 25

The rest of it is in the telnet window

The server typically responds with a 220 message

Type EHLO reciever.com


The server should respond 334 VXNlcm5hbWU6

Type  the username c2VuZGVyQHNlbmRlci5jb20=

The server will respond 334 UGFzc3dvcmQ6

Type  the password MTIzYWJj

If all goes well , the server will respond 235 Authentication succeeded

 You next need to send a message.

Type MAIL FROM: <sender@sender.com>

RCPT TO: <reciever@reciever.com>


FROM: <sender@sender.com>

Type any text you want , Please call me

Type <Enter>

Type .

Type <Enter>

Note: the last three are ENTER , PERIOD , ENTER on 3 lines.

Type quit to exit

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