For those of you concerned about the confidentiality of your personal information (and who isn't) and wish to check that your accounts haven't been compromised in a data breach, then there is an easy way to check thanks to Troy Hunt's fantastic online search tool Have I Been Pwned?
You can simply search on email addresses you own to see if any accounts using those addresses have been compromised. You can also get notified by the service should your email addresses appear in the latest data breaches.
Anyone who thinks they might be affected can check HIBP manually for their email addresses or account name. Anyone anxious about their email server credentials should change the password at the very least before going for a long, calming lie down.