He won a bronze medal in the half marathon at the 2023 World Athletics Road Running Championships in Riga.

[1] Mailu grew up the son of vegetable farmers, one of five children, in a village called Ulawani, not far from the Kenya-Tanzania border and Mount Kilimanjaro, although he himself did not live at high altitude.

He only started to train at fifteen years-old and stopped running until later in life after completing a college course to become a primary school teacher.

[3] Later that year Mailu finished as runner-up at the Frankfurt Marathon running 2:07.19 despite initially only starting the race in the role of pacemaker.

[8] Mailu was part of a Kenyan clean-sweep of the medals, alongside Sabastian Sawe and Daniel Simiu Ebenyo in the half-marathon during the World Road Running Championships in Riga, Latvia on 1 October 2023.