the secure:channel

Click here to read more about SpamStopsHere, the e-mail security company that brings you this blog.

In this multi-part series, I’m going to be covering the steps to take to isolate your e-mail problem so that you know which vendor to call. I will be focusing on companies that don’t have their own information technology team, but rather a coordinator that simply calls the appropriate vendor to resolve an issue. However, if you have your own e-mail server administrator, this information should also prove useful.

In part one of this series, we isolated the problem to your e-mail server’s public e-mail service and covered checking whether your domain name has expired and also if your DNS was configured correctly. We’re going to continue from there.

Connecting to your e-mail server to test connectivity

To test whether your e-mail server is offering public e-mail service, you’ll need to try connecting to it from outside the network where it is hosted. This will be easy if your e-mail server is hosted outside of your network, otherwise you will need to try a test from a remote computer. Note that testing it from home may not be viable, because the Internet service provider that you use at home may block your connections to remote e-mail servers for policy reasons.

From a Windows command prompt or a UNIX/Linux shell, you can use a telnet client to simulate a simple mail transport protocol, connection to your e-mail server. The simple mail transport protocol, also known as SMTP, is used by public e-mail servers to exchange e-mail. If your e-mail server is not offering SMTP service, it will be unable to accept Internet e-mail. Try the following command, where “mail.example.com” is replaced with your e-mail server’s hostname.

telnet mail.example.com 25

This is making a basic TCP connection to port 25 of the e-mail server, which is the Internet standard SMTP service port.You should get a response back from your e-mail server with a greeting starting with “220″ similar to the one below:

220 mail.example.com ESMTP

If the attempt times out before you get a greeting message, you should make sure that the problem isn’t at the site where you’re doing the test from. You can determine this by trying another connection to a third party e-mail server that you know will be up, such as this one at SpamStopsHere:

telnet test.relay1a.spamh.com 25

If the test to a third party server works but the one to your e-mail server times out, there is likely a problem with your network access rules. There is likely a firewall that is blocking the connections. If you can send e-mail to other users on the same e-mail server, it’s time to call the firewall administrator for the network where your e-mail server is located.

If you do get the greeting message from your e-mail server, the problem is with your e-mail server. Contact your e-mail server administrator. Optionally, you can try the additional SMTP service testing below.

Testing the SMTP service 

You can do more testing so that you can give additional information to your e-mail server administrator when you call. After you get the greeting message from the e-mail server, type the following additional commands, where “hostname” is the fully qualified domain name of the computer where you’re doing the test from, and the sender and recipient e-mail addresses are actual e-mail addresses that you are using for the test:

EHLO hostname
MAIL FROM: <sender@example.com>
RCPT TO: <recipient@example.com>
DATA
Subject: test 1

test 1
.
QUIT

Note that you should receive a response back after each command with a code that starts with the number two. If you get a response that starts with a number four or five it is an error message. Write down any error message and which command it occured after. This information will prove useful to your e-mail server administrator.

The second to last line above is simply a dot, also known as a period or full stop, on a line by itself. This tells the SMTP server that it is the last line of the message. After you type the dot, if you get a response that starts with a two, it means that the e-mail server has accepted the responsibility of delivering the message and the response will likely contain a message identifier that you will be useful in tracking what happened to the message after it was accepted. The following line is an example response with identifier:

250 2.0.0 m3IJSHbg019468 Message accepted for delivery

The e-mail server administrator should then be able to search through the e-mail server’s logs for appearances of this message ID to see what happened to the message.

Using an anti-spam service

If you use an anti-spam service, so that your DNS MX records actually direct people to send your domain’s e-mail to your anti-spam provider, and then your anti-spam provider sends the e-mail to your e-mail server after filtering, a few things are going to be different. When not using an ant-spam service, your email takes this path:

Public -> Your domain’s e-mail server

When using an anti-spam service, your e-mail takes this path:

Public -> Anti-spam service -> Your domain’s e-mail server

Your domains DNS MX records should include the hostnames that your anti-spam service provider assigned you, instead of your e-mail server’s hostname.

The above connectivity tests require that the anti-spam service be able to connect to your e-mail server successfully and deliver a message. Your anti-spam service will likely have a test button in the control panel that they offer you for account management where you can test this connectivity. If the connectivity test fails, more than likely your e-mail server is the cause. You’ll want to contact your e-mail server administrator. If the test is successful, it’s possible, although hopefully rare, that your anti-spam service is mistakenly filtering out your e-mail. Note that blank e-mail messages are often filtered out, so when sending a test message, be sure to type a subject line as well as a body.