The sustainability impact of e-commerce has increased, with the last mile being a key contributor. The sector is however struggling to tackle this impact, even though previous studies have tried to measure it. These studies have focused on one or two of the three pillars of sustainability. In this research, we define and implement a scoreboard to assess the sustainability of last-mile strategies in e-commerce. We evaluate the three pillars of sustainability using a scoreboard that can be implemented to quantify the impact of different last-mile strategies on sustainability. Results highlight the importance of this scoreboard, confirming its usefulness as the first one to integrate the three pillars of sustainability. Furthermore, through its application, findings highlight the importance of demand density when creating a sustainable last-mile strategy as it impacts on the economic (vehicle occupancy) and environmental (CO2 emissions and fuel consumption) pillars of sustainability. Furthermore, indirectly, the demand density also has an impact on the social pillar and the service level, although in a negative way.