Segment definitions vary by brand, but here are some common definitions: A hot segment are those subscribers that engaged with your email in the last 90 days. Warm could be email engagement between 91 days and 180 days, and cold is anything 180-plus days. You'll also want to segment out new to file, which are email addresses acquired in a defined period of time (e.g., the last month). These segments can be overlaid and used in conjunction with any demographic, domain-specific or persona-based segments you may already have. There are a great deal of additional important analytics that can propel an email program forward, but without more resources to translate analytics insights into targeting and creative, that may need to be a Q1 project.