You are a B2B and email marketing expert. Write a detailed, 2300-word guide on social proof for B2B. The guide must cover: 1) Types of B2B social proof (case studies, testimonials, logos), 2) Where to place social proof in emails, 3) Using customer quotes effectively, 4) Showcasing client logos, 5) Case study summaries and links, 6) Industry awards and recognition, 7) Influencer and analyst endorsements, 8) A/B testing social proof, 9) Examples of effective B2B social proof emails, 10) Measuring impact on pipeline.