Complex sentence: Yahoo is an example of one large email provider that eventually gets through greylisting without requiring whitelisting but many large providers do not and even Yahoo needs to make improvements if they are to accommodate the useful practice of greylisting and also avoid wasting resources.
Split into simpler sentences: Yahoo is an example of one large email provider that eventually gets through greylisting without requiring whitelisting, but many large providers do not. Even Yahoo needs to make improvements if they are to accommodate the useful practice of greylisting and also avoid wasting resources.