Can I import members to a global distribution list from a list of Display names or SMTP addresses?

I'm working with a large distribution list and the owner wants to import approx. 2400 users but only gave me their smtp addresses, which will not resolve by object name.  I can resolve these addresses in outlook client to display names but still will not resolve in AD by object name when I add a member.  What is the easiest way around this?  Thanks