We have had a couple of reports from customers whose systems are not working when trying to access the URL api.esendex.com or www.esendex.com by the URL’s IP address.  We have created re-directs on our website and this effects connections made by an IP address as opposed to using the URL. This change will only affect customers that do not have DNS set up in for their system to use.
If lack of a DNS describes your environment then have you tried updating the hosts file on your server? By adding a record for "www.esendex.com", it acts as a DNS lookup and will point any requests to our IP address but maintain the correct host header.

Simply add the following line to your hosts file (C:\Windows\System32\drivers\etc\hosts):

217.158.183.37    www.esendex.com
217.158.183.46    api.esendex.com

The configuration is relatively the same in a Linux/Unix environment. The host file is in the etc\hosts directory. Simply add the same lines above to the hosts file. If you chose you can also add an alias as well:

217.158.183.37    www.esendex.com   www
217.158.183.46    api.esendex.com           api

 
DNS is a service that is vital for internet connections and a service that is core to internet connectivity. However, we understand not all environments would necessarily have DNS so the workarounds above should help. If they do not or you would like to discuss your environment further please do not hesitate to call Esendex to discuss support@esendex.com or 0845 356 5759.