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Telnet for diagnosing email issues October 28, 2005

Posted by Al in : computers,Internet,networking,tutorial,utility , trackback

Sending Email Using SMTP & Telnet

If you are using Windows, you already have a Telnet client program which will automatically start if you replace the http with telnet in the URL address field of your browser.
If you want to start the Telnet client without a browser, it is located in your windows directory and is called TELNET.exe.

Most servers have a facilty called Simple Mail Transfer Protocol, SMTP for short, which is used for sending email.
SMTP is typically running from port 25 of your ISP’s servers so adding :25 to the end of a URL will connect you to the SMTP port.

To send an email using Telnet without a browser you will need to know the IP address of a server that has SMTP running.

There are various ways to find out this information, but thats another story. If you are using a browser you do not need to know the servers IP, it will be found automatically.

Sending Mail:
Open your browser and enter the URL:


This should fire up your Telnet client which you can customise if you like.

By default, you wont be able to see what you are typing.
To change this play around with the Telnet client settings.

You send emails by typing the following:
mail from:<youremail@yourisp.com>
rcpt to:<somebody@somewhere.com>
Subject:Enter a subject here
Type your message here.

Note that to send the email you need to put a fullstop on a newline and hit return.

That’s it, Simple Mail Transfer Protocol. SMTP using Telnet.


Retrieving POP Emails Using Telnet.

POP servers typically work on port 110, so to access the server, open your telnet client and connect to a pop.yourisp.com on port 110:
eg: pop.freeserve.com

If you are using IE type: telnet://pop.freeserve.com:110
This will fire up your telnet client automatically.

How to retrieve your emails

USER username
PASS password – Should produce an OK message and the number of emails.
LIST – Produces email reference numbers and size in bytes.
RETR email reference number – Will display header and body of referenced email.
DELE email reference number – Will mark the referenced email for deletion. The email will be deleted after you have QUIT the session.
RSET email reference number – Will un-mark the referenced email for deletion.
QUIT – Deletes any emails marked and quits your session.

That’s it, Post Office Protocol using Telnet.

Blatantly copied from here.


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