Distribution Issue

klone74

Hi we are going from mirapoint to exchange 2007 people that are using outlook on the old system have distribution list when we migrate them them over to exchange the distribution list do not more work when we try to send to a distribution list it says it failed and at the moment we are getting the end user to remake the distribution list and it works fine any clue why the old distribution list are not working any more?

o and we are going from outlook to outlook same version

Thanks.