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You get the call, “We’re not receiving any mail, can you come out now and fix it?”. Ever had one of these calls? It could be any number of reasons, but you can quickly eliminate a number of problems remotely in less that 5 minutes without having to rush over to the clients site, only to find the server is out of disk space, or the ISP is down.

 

The first thing to check, is that the clients IMC (Internet Mail Connector) Service is running and able to send email, and that the ISP or remote host is able to do the same.

 

Without going into too much detail about the SMTP protocol and the Internet Mail Connector, most email is sent through the internet via Port 25.  The receiving and sending application could be Microsoft Exchange Server, SendMail, an SMTP Relay Host or even Anti-Virus Software such as InterScan VirusWall.

 

The first thing we need to check is that the clients Exchange Server is still listening for email. Remember it does this on Port 25. You need to know the external IP address of your clients mail server. This will be something like 203.xxx.xxx.xxx.

 

Open a Telnet session from the run line to the clients IMC on port 25 by typing the following command –

telnet 203.xxx.xxx.xxx 25

 

Your Telnet session should open, and you should see a response from the clients server like this –

220 site.company.com Microsoft Internet Mail Connector 5.5.2650.21

 

Don’t worry if the response is different. We are basically looking for the 220 response.

 

If we get the response we know the IMC is up and running. If not, then the IMC Service may have stopped, thus stopping the recieval of email.

 

Now we are connected to the IMC and we know it’s running, we should test that mail is able to be sent from here to the ISP, and also from here to the Exchange Server.

 

To begin communicating with the IMC type the following command –

HELO site.company.com

 

You should see a response like this –

250 OK

 

Now we can send an email. We first need to say who the email is from. Let’s first check that the IMC is sending email internally to the clients Exchange Server. Type the following command –

MAIL FROM:<user@other.place.com>

 

You should see a response like this –

250 OK – MAIL FROM <user@other.place.com>

 

Now we need to specify who this message is being sent to. Make sure the address you are using is an actual valid address for the clients site. Type the following command –

RCPT TO:<client@company.com>

 

You should see a response like this –

250 OK – Recipient <client@company.com>

 

Now you need to tell the IMC you are ready to send data. Type the following command –

DATA

 

You should see a response like this –

354 Send data. End with CRLF.CRLF

 

You could send the message now without adding a Subject and Data, however, you may end up sending a few messages, so you will want to be able to tell them apart. We are now ready to add the Subject line. Type the following command –

Subject:test1

 

Now press the Enter key twice. You will not see a response to this command. The two enter commands are to conform to RFC 822.

 

Now you are ready to add your data to the message. Type in the following text –

Test from site.company.com to check connection

 

To send the message type a period at the next blank line. You should see a response like this –

250 OK

 

You can now close the connection. Type in the following command –

QUIT

 

You should see a response like this –

221 closing connection

 

Now you need to check with the client, that they received the email. If they did, then you can be pretty sure that any email that is received by their IMC will be sent to the user. It’s time to check the ISP!

 

To check the ISP, follow the above commands, but remember to replace the IP address of the clients mail server with that of the ISP when starting the telnet session.

 

You can also use the following procedure to test outgoing mail. However, due to the fact that your clients Exchange Server should be configured so it will not allow relaying of email, you will actually need to test this from your clients server.