Jasper is the strongest fit here because it is purpose-built for marketing copy, includes email campaign templates, and lets you generate on-brand promotional emails quickly with minimal manual effort. You can set your brand voice once and reuse it across every send, which cuts down the time spent on each campaign significantly. Copy.ai is a close alternative that also offers email workflows and a free trial if you want to test before committing. Claude Sonnet works well if you prefer a general-purpose assistant you can prompt with your product details to draft polished emails on demand. Gemini Flash is worth considering if budget is the priority, since it is free and fast enough for straightforward promotional copy.