1. One or more computer-storage media for use in a computing environment having thereon computer executable instructions that, when executed by one or more processors of the computing environment, cause the computing environment to perform a method of receiving an address book data structure sent from a first computing system to a second computing system, the method comprising: receiving the address book data structure at the second computing system, the address book data structure comprising: a header field, the header field comprising: a version field specifying at least the type of the address book data structure; a signature field comprising a signature field cyclic redundancy check (CRC); and a records field; and a meta-data field, the meta-data field comprising: a size field; and an entry attribute table, wherein the entry attribute table comprises a list of a plurality of property identifications, the property identifications in the entry attribute table representing each of the properties that would be present in a fully populated address book entry, and wherein the each of the property identifications in the entry attribute table define a particular encoding type for each of the properties; one or more address book records; and a presence bit array contained within the at least one of the one or more the address records, the presence bit array indicating each property which is identified in the entry attribute table and which is also present in the at least one of the one or more address records and the presence bit array further indicating each property which is identified in the entry attribute table and which is not present in the at least one or more address records; and calculating a calculated CRC for the address book data structure; comparing the calculated CRC to the signature field CRC; and determining from the comparison whether there has been corruption of the address book data structure.