Segmentation allows you to divide your email list into subgroups based on specific criteria. Here are some common segmentation criteria: - Demographics: Age, gender, income level, education. - Geographics: Location, climate, urban vs. rural. - Psychographics: Lifestyle, values, interests. - Behavioral: Purchase history, website activity, email engagement. - Firmographics: Company size, industry, job role (for B2B).