When you attempt to duplicate a mailbox in a site that is a member of a
distribution list which is homed in another site, the following error
message appears after the associated Microsoft Windows NT account has been
selected.
This object has not yet been completely replicated or cannot be changed
from this connection. Try connecting to a Microsoft Exchange Server
computer in the same site as this object.
Microsoft Exchange Directory
id c1010ac1
When you click OK or Apply, the following error message appears:
The object "<Mailbox name>" with directory name "<alias>" already
exists. Enter a unique name on the general property page for this mail
recipient.
Cancel is the only acceptable response to avoid the previous error
messages. The mailbox has already been created. It will function as a
normal mailbox but will not be on the foreign distribution list.