As a developer myself, I definitely understand the need for standards and the desire to follow them. However, if they come at the expense of usability, either the standards are bad or you haven’t implemented them properly. Instead of using lowest and low, why not lowest and medium? At least that would provide more contrast. Better yet, let users pick their levels - even if limited to those 5. Until some substantial change is made to make it usable again, I’ll be sadly searching for my next email app.