This song appears in the Sam Henry Collection #827. Sam Henry's 'Songs of the People' page 100 where it is called Yellow Meal.The sources were local and Manus O'Connor's 'Irish Com-All-Yes' In fact the word meal/mail means both simultaneously. As I point out in my "Thousands are Sailing: a brief song history of Irish Emigration"(1994)

"The song tells a story typical of the experience of many emigrants; they were lied to. The pronunciation of 'meal' allows it to be mistaken for 'mail'. The Emigration agent would do nothing to discourage the emigrant from thinking he had bought passage in a fast mail boat."
"The Tappscott brothers were perhaps the biggest rogues on either side of the Atlantic; one who sold passages unscrupulously in Liverpool; the other whose runners (touts recommending boarding houses) met the emigrants on the other side and fleeced them of whatever they had left. They may be read about in Terry Coleman: Passage to America (Penguin, Harmondsworth, 1974). Many Irish people went to Liverpool to emigrate because it was cheaper but they paid in other ways."