Exchange error 9325: OABGen will skip user entry 'username' in address list '\Global Address List' because the SMTP address '' is invalid. - \New Offline Address Book

If you get the following error message for an account that should not have an email address 

PVM-LON-MBX01		9325
MSExchangeSA		OAL Generator
Application		09/01/2014 14:03:57
Error (Info)		3285482
OABGen will skip user entry 'username' in address list '\Global Address List' because the SMTP address '' is invalid. - \New Offline Address Book

then do the following

start ADSI Edit (on a domain controller)

navigate to the user with the issue

right click and properties

navigate to the attribute 'showInAddressBook'

remove all entries from this