The ‘migrant letter’ has been proposed as a separate genre of letter-writing around features concerning absence, identity and relationships and location. However, questions arise about this claim, made using largely North American material. Explored in a different context, important complexities and differences come into view. This is discussed regarding the settler colonial context of South Africa using data from the Forbes family collection, containing around 15,000 documents written between 1850 and 1922. The Forbes were Byrne migrants to Natal, then Transvaal. The majority of letters in the collection were written and exchanged within South Africa, with significant numbers from family members remaining in Scotland or who removed elsewhere, and many drafts and copies of letters written by the South African end exist too. The size and composition of contents enable migrant letters to be explored within the greater entirety of the family’s letter-writing, conceived as a scriptural economy with characteristic writing practices. This is examined by looking in detail at the writing practices of a range of letter-writers and their correspondences. Important differences concerning how absences, identities and relationships and locations are inscribed in the context of South Africa are explored and traced to features of its settler colonial mode of production.