"we took immediate steps to lock down our email service and eliminate any threat to our 350,000 eircom.net email users" The company said.
The company said they found no evidence suggesting that the Inruders have gained access to any other systems or services including customer data.
They also recommend their customers to change their email accounts passwords and on a regular basis in the future. If you have used the same password anywhere else, it is better to change their also.
After implementing a number of system modifications, access to eircom.net email had been fully restored.
The company said it is still trying to find out the cause of intrusion and had alerted relevant bodies including the Office of the Data Protection Commissioner.