Why does a connection to SMTP fail?

Command Line Email FAQ—simple answers to complex questions.

My question

• Q: When I am trying to send an email from the command line, an error message appears: "An established connection was aborted by the software in your host machine". What is the problem and how can I fix it?
• A: Most likely, the connection is terminated by a Firewall or an Antivirus that is running on your local PC. In rare cases, this happens when connection is terminated by software, which is running on remote the host.

Telnet?

To test connection, try connecting to the SMTP server with a telnet client. Telnet usually is not blocked by a firewall software.

Telnet application is not available by default. You have to enable telnet client once, or otherwise, you will receive the error message: 'Telnet' is not recognized as an internal or external command, operable program or batch file.

How to telnet SMTP server?

First, start the Command prompt. In the CMD window enter: telnet smtp.example.com 25 and after, enter helo testing in the console.

If a connection was successful, the server should return code 220 with an optional greeting message. After helo command, the mail server responds with code 250.

If SMTP server is accessible from telnet as shown in example, then inability to email via febootimail is likely caused by the Firewall or Antivirus software. Try allowing febootimail.exe in the firewall settings.

Note that while in telnet, it is not allowed to use backspace. If a mistake is made while typing commands, the whole line should be retyped without making any corrections.

This article may be referenced as (KB ID: 514).

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