He was allegedly among the Western barons summoned to Inverness in 1427 to meet King James, who promptly seized them on arrival, executing some and imprisoning others.
The king sent Mackenzie, then a mere youth, to the High School at Perth, regarded at that time as the principal literary seminary in Scotland.
According to traditional histories of the Clan Macrae, he was prevailed upon by Fionnla Dubh mac Gillechriosd to return from school in order to deal with three illegitimate uncles, who were disturbing his tenants in Kinlochewe.
It is said that an account of their conduct soon spread abroad, and reached the ears of the Chief of Kintail, who at once with a party of six hundred men, passed into Sutherland, where, the Earl's followers having joined him, he defeated the invaders, killed a large number of them, forced the remainder to sue for peace, and compelled them to give substantial security for their peaceful behaviour in future.
According to the Earl of Cromartie, he intervened to assist Allan Macdonald of Moidart (with whom he had previously been at loggerheads) against Allan's brother, who had usurped some of the Moydart estates, and there are also traditional accounts of his involvement in about 1452 in the Battle of Bealach nam Broig between a western force of MacIvers, Maclennans, Macaulays and Macleays against a force of Frasers, Munroes of Foulis and Dingwalls of Kildun.
The weight of traditional clan history is to the effect that he married, first, Anna, daughter of John Macdougall of Dunollie, and, secondly, Margaret, daughter of Macdonald of Morar (a cadet of Macdonald of Clanranald), but Aonghas MacCoinnich has pointed out the difficulties which Alexander's supplication for dispensation in 1466 (referred to above) presents for the traditional account.
The date of Alexander's death is uncertain, though it is clear that he had died by 1488,[8] since his eldest son was served heir in the lands of Kintail at Dingwall on 2 September 1488.
[9] Aonghas MacCoinnich suggests that Alexander may in fact have died by July 1479, as his son was by then already being held responsible for rental payments in the king's dukedom of Ross.