Name could not be resolved error.....

[SideShowBob]

Hi
Have a strange problem, where I can set up mail accounts,
and use these fine, but if I try to add a mailbox in the
Open These Additional Mailboxes field, I immediately get
an error "The name could not be resolved. The action could
not be completed"

This is before ive even tried to resolve a name, its as I
click Add, the error just appears, so you dont even get a
chance to put a name in there.

Any ideas what could have caused this? it seems to be
after we ran the move server wizard and moved the server
with these accounts on into a new site.

Thanks
Graham