This is a problem that I ran into on a recent CP install. Customer wanted 100 range DN's. When I went to build Mailboxes 110 thru 119 I would get the NAME & SPECIAL PREFIX error.This from Thread799-709839. Luckly I had printed it and put in my programming notes. Resolution: This can be resolved by configuring the CP to be VM, once up and running, go into the browser and change it to CP Interface, change the NAME & SPECIAL PREFIX from 11 & 19 to 80 & 81, Under system Properties. You may have to change the Park Prefix or Line Pool codes and other codes to a different number.This particular install I didn't have to. All is working well.