Note: this month has been one of the busiest I’ve had in the last two years. It’s been very hard on work and that’s the reason I’ve not been posting as frequently as I’d like. In fact, next week will be worse because I’m a speaker at the Microsoft’s worldwide presentation event of Visual Studio 2008, Windows Server 2008 and SQL Server 2008, so I will be travelling for the whole week. I hope that I can post something however. At least I’ll try my best. :-)

This is a little bit technical post, but if you follow the steps one by one it will be easy to put into practice. Let’s go!

Sometimes you’re not able to deliver a message to a recipient and you get some strange code from your Outlook (or the e-mail client you normally use) or, simply, get your e-mail bounced back. What everybody generally does is call her system administrators in search of help. But you will earn a lot of time and knowledge if you can find the problem by yourself (and you’ll save your busy sys-admin some health too) . Let’s find out how to do it...

Open your command line tool typing “cmd” in your Start·Run menu:

The first thing we’re going to do is check what are the servers responsible for handling e-mail for the problematic recipient.

The destination domain is just the text after the '@' of your recipient’s e-mail address, so that if it is johndoe@yourcustomer.com, the domain would be yourcustomer.com. Type the following command in the command line window:

nslookup –type=mx recipientsdomain.com

using the correct domain. You will see something like this:

The information you get that starts with the text ‘MX’ (short for Mail eXchanger) indicates the server responsible for handling the e-mail of the domain. In big domains usually there are more than one of them, but you should normally check only against the one with the 10 preference, as indicated.

OK, now that we know the server we must check, it’s time to connect to it. In the command line type the following:

telnet mail.yourcustomer.com 25

using the server you’ve just found out.

25 is the standard port for e-mail communication. If the server is up (and your connection too) you’ll see something that starts by the number ‘250’ (which means ‘this is OK’), like this:

If there is not a connection with the server you’ll get an error:

And you then will know that the reason of your problems is that the server is not working at all.

If you succeed it’s time to check the validity of the e-mail account. Type the word ‘ehlo’ following the domain name of the sender e-mail address. You’ll get a series of 250 acknowledge messages:

Now type 'mail from:' using the sender e-mail between ‘<’ and ‘>’ signs:

Next type ‘rcpt to:’ with the recipient’s e-mail address in this server. If the e-mail address exists and is willing to receive your email you’ll see something like this:

This will mean that, in this moment, there is not any problem with the recipient’s e-mail so you can retry the sending now.

But if there is a problem with the e-mail -which is very probable and that’s the reason you started all this stuff in the first place- you will get an error code (a number not ‘250’) and a message telling you the which the problem is all about. For example, if the e-mail address no longer exits you’ll get:

That’s all. You have diagnosed the problem by yourself and will be the super-geek hero of your office :-)

Don’t forget to type ‘quit’ to exit the telnet program before leaving. And never mind: if the address is OK your recipient will not receive any message from you and will never know that you have made this check procedure.

A professional e-mail marketing program such as MAILCast will offer you detailed information about the cause for some mails to bounce back, but if you are just sending a small bunch of e-mails from your “normal” e-mail client, with this technique you can found the main cause by yourself.