Currently it seems Outlook.com has blacklisted our IP causing it to drop all mail from us send to Outlook.com mail accounts. Unfortunately mail is also not delivered to the spam folder and whitelisting our mail address is not working either.
We have reported this to Outlook.com and are waiting for them to reply.
Outlook.com has reviewed our IP and will liberalise the anti-spam measures taken within 24-48 hours. This will probably mean mail should start working again soon, however mail might be delivered to the spam folder instead of the inbox.