A realistic large document envelope mockup for corporate stationery, one ivory paper envelope with a clean blank front panel reserved for branding, subtle paper grain, crisp flap and folded edges, placed on a warm light-gray studio surface, three-quarter top-down product view, soft daylight from the upper left, gentle contact shadow, 50mm lens perspective, minimal premium stationery presentation, neutral ivory, charcoal, and muted blue palette, no readable addresses, no real logos, no personal data, no watermark. editorial poster design, portrait 4:3 composition, designed for a prompt gallery thumbnail, immediately recognizable, clean commercial presentation.