This short article covers how to test SMTP Connection to
Mail Server using
- TELNET Installed on client
- Network flow from the client server and Mail Server should be Open
First we will launch
telnet on the
port listening for mail application on the SMTP Server. It can be port 25,465 or 587. We will be using port
telnet <mail server DNS/IP> <port>
The next command we will execute is
HELO. This is a greeting message that will start the communication between
TELNET Client and
Mail Server. We should also specify the domain we will be sending the mail from.
You should obtain something similar to the following output:
250-<mail server DNS> says hello 250-STARTTLS 250-ENHANCEDSTATUSCODES 250-PIPELINING 250-CHUNKING 250-8BITMIME 250-XACK 250-XMRG 250-SIZE 54525952 250-VERP 250 DSN
Or something like this depending of the SMTP commands the server accepts:
250-STARTTLS 250-8BITMIME 250 SIZE 53477376
Then we use the
Mail FROM command which will determines the address to which bounces are sent.
MAIL FROM: <test@Domain.com>
Check if you have inserted the angle brackets if you encouter Syntax Error in Mail Command.
Ensure that the domain you are using is registered on your mail server as variations can cause errors to appear.
Now that the
MAIL FROM command has been sent, we will issue
RCPT TO command which will indicates the server what will be the recipient's address (always cross-check the destination mail address).
RCPT TO <test2@Domain2.com>
Before starting the body of the mail, we will send the
DATA command. It will let the SMTP Server know that everything else will be the Body of the message. This is where we will also specify the headers to be sent.
We will leave a blank line between the Headers and the Actual body.
To tell the Server the message is completed we will leave a blank line and insert "." on a blank line. If you need a "." on a line by itself, you should use ".."
DATA From: "Test" <firstname.lastname@example.org> To: "Test2" <email@example.com> Subject: Test MAIL Hello, Here a test mail regards .
250 should be obtained.
Now that the mail has been queued, it will go through the SMTP Server and will be in your inbox if is it successful.