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Network Testing and Emulation Solutions

Layer-4 SMTP Traffic to a Mail Server

Goal: Create un-authenticated, un-encrypted SMTP traffic to an email server.

This is a basic email traffic testing scenario. We start with an easy-to-construct scenario for a mail server (no user authentication or TLS configured). This testing scenario works when
  1. the mail server accepts emails from a local network (E.G.
  2. or the email server allows incoming mail to its own domain.

The following scenario was tested against two postfix servers:

  1. LANforge sending to an email relay in an office firewall to a public email server. The public server permits the IP of the office firewall and all email addressed to
  2. LANforge sending emails directly to the mail server, skipping the office gateway.

Please remember that you cannot actually send things to, see RFC 2606, Section 3. You will want to assemble your own mail domain records and email server as necessary. If you are using Postfix, you can start with these guides.

CAVEATS: This cookbook does not cover authenticated SMTP connections (E.G.: Postfix and SASL) or SSL/TLS certificates (E.G.: Postfix and TLS).

  1. Create a text file /home/lanforge/email-body.txt. We will send it as an email. We will use a minimum of RFC 822 specified fields: To, From and Subject screenshot

  2. In the LANforge Layer-4 tab, click Create and enter fields we will use to find the email body and where we will send it. screenshot

    1. Set the Name to email1

    2. Set SMTP-FROM to

    3. The RCPT-TO address to

    4. For UL/DL, choose Upload

    5. Our mail relay is at outbound.candelatech.local. Enter the URL smtp://outbound.candelatech.local

    6. Set Source/Dest to email-body.txt. Double check that files actually exists at /home/lanforge/email-body.txt

    For more information see GUI User Guide: Layer-4

  3. To monitor your mail relay, open up a terminal, ssh to the relay and tail the mail-log. You will probably use the command sudo tail -f /var/log/maillog

  4. In the Layer-4 tab, select connection email1 and click Start.

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