SMTP HELO/EHLO Commands
SMTP
HELO/EHLO Commands
The HELO/EHLO can be very
helpful in case you wanna know what happens when you hit the SEND button to
send a mail. So, in this post we'll work on sending a mail from the command
prompt using the TELNET command. They are also some very useful commands that can
be used while troubleshooting SMTP errors.
HELO (Hello)
The client sends this
command to the SMTP server to identify it and initiate the SMTP conversation.
The domain name or IP address of the SMTP client is usually sent as an argument
together with the command (e.g. “HELO client.example.com”). If a domain name is
used as an argument with the HELO command, it must be a fully qualified domain
name (also called FQDN).
EHLO (Extended Hello)
Same as HELO but tells the
server that the client may want to use the Extended SMTP (ESMTP) protocol
instead. EHLO can be used although you will not use any ESMTP command. And
servers that do not offer any additional ESMTP commands will normally at least
recognize the EHLO command and reply in a proper way.
In windows 7 make sure to
enable TELNET command from Windows Components.... http://blogs.technet.com/b/ferris/archive/2010/05/03/howto-enable-telnet-in-windows-7-and-vista.aspx
* Open command prompt using
Admin credentials
*Type Telnet
mail.teamxchange.in
In case you receive the
following error: Connecting To mail.server.com....Could not open
connection to the host, on port 25: Connect failed
This simply means the
server that you're trying to work upon has secured port 25 and uses a different
one or you have typed the incorrect mail domain name.
In case the settings are
correct the reply should in the following format:
220-mail.teamxchange.in
ESMTP
220 Welcome to
Now, we’ll connect using
the HELO as well as EHLO commands and see the outputs.
Type HELO
The server here will reply with: 250
SMTP.teamxchange.com(meaning a connection has been made with SMTP
server or the First Point of Contact server for the domain)
The EHLO command is a bit
descriptive when called as its encrypted and Extended SMTP.
Type EHLO
The server here will reply with:
250-smtp.server.com
250-SIZE 1000000
250 AUTH LOGIN PLAIN
CRAM-MD5
Now, authenticate using
your ID and password but in BASE64 format.
Type:
AUTH LOGIN
334 VXNlcm5hbWU6(Here, the server has
replied asking for the username in BASE64 encoded text)
We’ll reply the same using
BASE64 format
Adlxdkej (Here we have replied
with our username in BASE64 format)
334 UGFzc3dvcmQ6 (Here, the server is
asking for the password in BASE64 encoded text)
lkujsefxlj (Here we have replied
with our password in BASE64 format)
235 2.7.0 Authentication
successful
Please find below the link to
encrypt or decrypt data in BASE64 format:
So, now as we are
authenticated, we’ll try to send mail.
Type MAIL
FROM:
250 OK (Here the server has
recognized the sender's id)
Type RCPT
TO:
250 OK (Here the server has
recognized the recipient's id)
Type DATA (this
command is to ask the server to allow user to type content of the message)
354 Send message content (Now you can start typing
the body of the message)
Type THIS IS A TEST
MAIL (the mail body)
Type Subject: TEST
Mail
. (The “.” Here indicates the
send command)
250 OK, message accepted
for delivery: queued as 12345
Type QUIT
221 Bye
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