Please find the following steps and SMTP commands to test SMTP communication using Telnet on Port 25.
1. At a command prompt, type telnet, and then press ENTER. This command opens the Telnet session.
2. Type set localecho and then press ENTER. This optional command lets you view the characters as you type them. This setting may be required for some SMTP servers.
3. Type set logfile <filename>. This optional command enables logging of the Telnet session to the specified log file. If you only specify a file name, the location of the log file is the current working directory. If you specify a path and a file name, the path must be local to the computer. Both the path and the file name that you specify must be entered in the Microsoft DOS 8.3 format. The path that you specify must already exist. If you specify a log file that doesn't exist, it will be created for you.
4. Type open mail1.fabrikam.com 25 and then press ENTER.
5. Type EHLO contoso.com and then press ENTER.
6. Type MAIL FROM:firstname.lastname@example.org and then press ENTER.
7. Type RCPT TO:email@example.com NOTIFY=success,failure and then press ENTER. The optional NOTIFY command defines the particular delivery status notification (DSN) messages that the destination SMTP server must provide to the sender. DSN messages are defined in RFC 1891. In this case, you are requesting a DSN message for successful or failed message delivery.
8. Type DATA and then press ENTER. You will receive a response that resembles the following
9. Type Subject: Test Sampleand then press ENTER.
10. Press ENTER. RFC 2822 requires a blank line between the Subject: header field and the message body.
11. Type This is a test message and then press ENTER.
12. Press ENTER, type a period ( . ) and then press ENTER. You will receive a response that resembles the following:
13. To disconnect from the destination SMTP server, type QUIT and then press ENTER. You will receive a response that resembles the following:
14. To close the Telnet session, type quit and then press ENTER.