3.9.12 AlternateType

The Alternate element is an optional child of several of the above destination types. It contains another destination, to which delivery may be attempted if delivery to the parent destination is unsuccessful. Note that the destination in the Alternate may in turn have an Alternate, creating a series of backup destinations (maximum depth 16). In general, an Alternate should be of the same type of destination as the parent (e.g. fax alternate for a fax destination), since document types and options for different sorts of destinations are unlikely to be compatible. An Alternate address is somewhat restricted, due to the internal representation of address data, in that it may not contain insert data, or properties in any segment other than the default ("USER") segment.