Exchange Server

Test SMTP Service in IIS and Exchange

How can I test to see if my SMTP service is ready to receive incoming mail?

There are a couple of ways to verify if the SMTP service is working properly:

Testing with an e-mail client

First, you can choose to use a standard Internet e-mail client program, such as Microsoft Outlook Express, for a quick verification. Locate the place where you can specify the outgoing e-mail (SMTP) server and change it to the domain name of the new SMTP server. Send a test message to your regular e-mail address and verify its delivery.

Sponsored Content

Passwords Haven’t Disappeared Yet

123456. Qwerty. Iloveyou. No, these are not exercises for people who are brand new to typing. Shockingly, they are among the most common passwords that end users choose in 2021. Research has found that the average business user must manually type out, or copy/paste, the credentials to 154 websites per month. We repeatedly got one question that surprised us: “Why would I ever trust a third party with control of my network?

Note: There are many small e-mail clients made for the purpose of sending e-mail to mail servers without needing to configure them with e-mail accounts (like you need to do with Outlook Express for example). You can use any of these small (and mostly freeware) programs for fast troubleshooting.

You can also use a small tool that does not require installation:

  • Ghost Mail 5.1

Testing with the Pickup directory

You can also compose a simple e-mail text file based on the SMTP specifications (RFC 822). Here is the content of a sample text file typed in Notepad:

From: [email protected]
To: [email protected]
Subject: testing

This is the test message body.

Simply copy or move the text file into the Pickup directory where SMTP was installed. (The default path should be “‘Inetpub’mailroot’Pickup” but if you have Exchange installed then the path will be “‘Program Files\Exchsrvr\Mailroot\Vsi 1\Pickup”.)

The SMTP service periodically checks into the Pickup directory and will attempt to deliver any of the messages found in the directory. Verify if you can receive the test message from the destination mailbox.

For more information about the RFC 822 specification for a properly formatted message, refer to The RFC 822 Message Format.

Testing with Telnet

You can also use TELNET to test your SMTP service. SMTP uses port number 25, so in order to use telnet to open an SMTP session with an Exchange server we use the command

​telnet 25

If the connection is successful, we should see a banner and a command line interface. We then need to follow RFC 821 for the accepted SMTP commands, which are quite simple (as the name says…)

​220 Microsoft ESMTP MAIL Service, Version: 5.0.2195.5329 ready at Sun, 15
Sep 2002 23:51:06 +0200
250 Hello []
mail from: [email protected]
250 2.1.0 [email protected] OK
rcpt to: [email protected]
250 2.1.5 [email protected]
354 Start mail input; end with .
subject: this is a test
Hi Daniel
I'm trying to test this connection from Telnet.
Let me know if you get this message.

250 2.6.0  Queued mail for delivery
221 2.0.0 Service closing transmission channel

Connection to host lost.

Press any key to continue...

(Screenshot of the same dialog)

Related Topics:

13 Email Threat Types to Know About Right Now

As email threats evolve and multiply, keeping track of them all—and staying protected against the many different types—becomes a complex challenge. Today, that requires more than just the traditional email gateway solution that used to be good enough.

In this eBook you will learn:

  • What are the most common and challenging email attacks for organizations?
  • How to defend against sophisticated email threats, such as spoofing, social engineering, and fraud
  • How to protect employees at the inbox level with the right technologies and security-awareness training
  • How to use a multilayered protection strategy to reduce susceptibility to email attacks and better defend your business and employees

Sponsored by: