Where is the recipient data stored? (i.e. what is the data source?)

Did you used to be able to edit it?

If it is in an "Office Address List" (OAL) created in Word, you should be
able to edit it unless the structure of the OAL (which is an Access/Jet .mdb
format database) has been changed, in which Word will not recognise it is an
OAL and will not let you edit it.

Word will not let you edit many types of data source via this dialog - e.g.
if you have an Access /Jet database that is not an OA, you will need to use
Access to edit it, or perhaps some other program that knows how to edit that
file.

Peter Jamieson