email@example.com addresses have been depreceated for the last 6 years or so. The MX for skynet.csn.ul.ie has been removed, this means that mails to these addresses will no longer deliver. Basically, you should be using either firstname.lastname@example.org or email@example.com, which is up to you. If you aren't already, you need to change. Bear in mind subscriptions to mailing lists etc may need to be fixed too.