Letter-Sized Mailers & Envelopes

Our Letter range is made up of cardboard envelopes and flat mailers designed to fit within Royal Mail's Letter postal specifications (max 240 x 165 x 5mm, up to 100g) — the cheapest UK postage tier. Ideal for sending greeting cards, documents, photographs, thin printed materials, and flat product samples, our letter mailers are rigid enough to protect contents in transit while staying slim enough to qualify for Letter-rate postage. Choose from board-backed envelopes, all-board mailers, and peel-and-seal designs in a range of sizes and finishes. For thicker items, see our Large Letter mailers and Small Parcel packaging, or browse our full Royal Mail postal sizes guide.