Manipulate email addresses in AD

We have a tricky problem. For legacy reasons, many of our (2000+) users have our default email address of @bedfordschool.org.uk but also the legacy @bedfordschool.org

I need to remove the legacy bedfordschool.org . . . . (as we are moving users to Office 365).

I have toyed with DSQuery user and DSGet user . . . but

1. dsget user -email only seems to return the default email address, not all emails for the user.
2. Even if I can find the users who still have the legacy email, I can't think of any way of removing that - and string search for bedfordschool.org will of course also find the bedfordschool.org.uk

Any ideas please? I'm not skilled at scripting nor VB etc.

thanks,

Bob