Adds a MIME X-field onto an item. This allows third-parties to store data onto any item in a key/value pair.
AFTKN_ITEM_ADD_MIME_XFIELD or 930
VOID ItemAddMimeXField( ANSISTRING MessageID; ANSISTRING XFieldName; ANSISTRING XFieldValue)
Unique item identifier, returned by ItemMessageIDFromView().
The name of the X-FIELD to set. For instance, “X-MYADDIN-SOMEVALUE”.
The value of the X-FIELD to set. This can be any string value that is meaningful to your application.