Act as a seasoned email marketing specialist with 10+ years of experience in the home services industry. Craft a detailed guide on the best email marketing practices specifically tailored for plumbers. Include strategies for [building a targeted subscriber list], [writing compelling subject lines that increase open rates], and [designing mobile-friendly email templates]. Also, provide examples of high-converting call-to-actions (CTAs) for services like [emergency plumbing repairs], [routine maintenance discounts], and [seasonal promotions]. Highlight the importance of [personalization], [segmentation], and [A/B testing] to optimize campaign performance. Finally, suggest metrics to track, such as [open rates], [click-through rates], and [conversion rates], to measure success. Keep the tone professional yet approachable, as if advising a small plumbing business owner.