Diagnose Email Server Problems with Free Tools

Dave Drager 09-03-2008

If you are having problems with your email server; there could be any number of issues which could be at the root of the problem. However, most e-mail issues fall under 3 main categories: Email Server Problems, Spam Blacklist Entries, and DNS Problems.


1. Email Server Problems

If your mail server is misconfigured or otherwise has system problems, there is not much you are going to be able to do about this. You’ll need to contact your system administrator and have them look into the problem. One of the best ways to narrow down a configuration issue is to watch the mail log for errors, usually the problem will be revealed in the logs.

2. DNS Problems

If your domain’s DNS has been misconfigured, this can cause a lot of email problems. There is a simple way to check your DNS entries to see if external servers can find your e-mail server. Free Service

This service will let you type in your domain – this is the part after the @ in For this example we are going to use

Type the domain name in the web page, make sure “maximum details” are checked, and then click “Check”.


This will load a page which transverses your DNS for that domain, and ultimately try to connect to the mail server. A successful mail server entry will look like this:


3. Your server has been DNS Blacklisted

If your server has been sending out spam, maybe even on a different domain, it can cause your IP address to be blacklisted. When sending an email, if you get a rejection mail back that states you are on a spam blacklist, then this is the cause of your email woes.

Many email servers use Realtime Blackhole List (RBL) servers to cut down spam drastically. One of the most popular services is SpamCop.


Use to check to see if your domain has been blacklisted.

Enter your site into the OpenRBL IP/Domain box:

openrbl input

Press enter to update the page.


Then click the green button which says “Openrbl JS Client”

openrbl submit

It will then use Javascript to query a number of DNS based blacklist servers and present you with the results. Blue is best and means your IP has been “whitelisted” as a known good domain. Green is good as it did not return any results (good or bad). Red means that the server thinks your ip is sending spam and any mail server which checks against this blacklist will either reject your message or have a greater chance of tagging it as spam!

Below is a sample result:


openrbl results

Click on each blacklist server to see a more detailed example of it’s response. In the above example – when you click on APEWS RBL server it states that this is a false positive and gives you links to do further testing.

In conclusion – email is a complicated system where anywhere along the line problems can pop up. Some other common email problems involve domains over quota, incorrect email client configuration, and temporary internet issues. Using the above sites should help you narrow down many of the problems your email server may be having and give you a good idea as to which direction you need to investigate further. If you have not been able to track down the problem you are having, send any information you have found to your e-mail administrator!

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  1. Pin
    April 11, 2009 at 8:22 am

    Some email setup to have all services (POP, IMAP, SMTP, Webmail, etc) installed in a single server. This is bad!

  2. Dave Drager
    March 11, 2008 at 7:18 pm

    Test (please delete)