is a free service to check if your IP address is blacklisted, a common cause of email delivery issues. Only a small number of blacklists affect your email delivery. With, you can find out if you're on any of the blacklists most relevant to Ireland.

What is an IP address?

An IP address (Internet Protocol address) is a unique address that computers and other devices use in order to identify and communicate with each other on a computer network. An IP address simply identifies a specific computer on a network. More FAQs...

About IE Internet

IE is a leading Irish technology company that provides managed email and application hosting services for business. is a service we have developed with the needs of our customers in mind.

This is work in progress.. I will try add a bit to it each week based on my personal experience

General Info

Please note the below advises are applicable to typical company's outgoing mailserver. I am not going to provide support information to spammers or newsletter providers.

If you ever experience any issues with delivery of your emails to recipients mailboxes you need to find out what exactly is causing this issue and how serious it is.

Below I present my own email delivery troubleshooting plan:

1. You need to determine whether the recipient mail server does accept the message or if it does reject it.

Check your outgoing mail server logs to see what has happened to the message, assuming the recipient domain is fine and MX records are correct it can be either:

- 4xx rejection - usually just temporary rejection, often used by greylisting techniques. In many cases the rejection message will give you a clue, like ie. wait 10 min and retry.

- 5xx rejection - permanent rejection. Your IP or domain name is most likely blacklisted (public or private blacklist). 

- message accepted - now you need to find out what has happened with the message as it has either been delivered to some spam/junk folder or discarded by recipient's mail server (I would always strongly advise against any type of silent discarding).