In the jurassic period of the Irish internet - say in the early 2000s - there was one email provider of choice for Irish people. It was eircom.net. Like aol in the US, thousands and thousands of people used Eircom emails to communicate.Eventually better email providers like Gmail came around and a lot of people moved on from eircom. However for a certain kind of person born before 1980, there is still a bit of romance around the eircom email address. For them it's like a first car or first girlfriend. It brings them back to a simpler time of communication.
In recent years, Eircom became Eir but many people hung onto their eircom.net email addresses. Well there's some bad news for people like your parents who might still use eircom for email, as it's been reported today that Eir will soon be charging users €5.99 per month to use its service. That's basically €75 a year to spend on email when there's loads of free providers out there.
The fee will be introduced in late March. Tell your parents that if they don't pay, their account - and all of their emails! - will be deleted in 60 days. It might be time to migrate.