Cardboard Envelopes

RAJAPACK UK's cardboard envelopes and mailers are made for post-room teams, office managers, e-commerce despatch operations, and print and framing businesses. They help you send documents and flat goods through the post without bending, creasing or corner damage. From rigid board-backed envelopes and do not bend envelopes, to expandable capacity mailers, we stock everything you need to protect flat and semi-rigid items from despatch to doorstep.

Whether you're posting certificates, contracts and legal documents, or despatching books, magazines, prints and photographs, our cardboard and hard backed envelopes are the right choice for any business. Each one is designed to stay flat under normal courier and Royal Mail handling. Our range of cardboard backed envelopes are made from recyclable and recycled materials, so you protect your contents and your sustainability commitments at the same time.

Our range covers:

• Board-backed 'do not bend' envelopes - a rigid card backing keeps documents flat, pre-printed with 'Please do not bend'. Available in six popular sizes for certificates, contracts, and A4 and A5 paperwork.
• Rigid cardboard mailers - all-board envelopes including rigid cardboard envelopes with long edge openings or a rigid mailer with a short edge opening for books, magazines, DVDs and prints that must not fold in transit.
• Capacity mailers - deeper cardboard mailers that expand to fit thicker items such as catalogues, books, games and phones.
• Tamper-evident cardboard envelopes - locking-flap formats that show clear evidence of interference, for confidential or high-value paperwork.
• Self-seal adhesive envelopes - peel-and-seal cardboard envelopes that close quickly without tape for faster despatch.
• White and brown cardboard envelopes - choose white cardboard envelopes for branded or premium presentation, or economical brown board for everyday post-room use.

Key features and benefits:

• Protect documents from bending and creasing - a rigid board or card backing keeps certificates, contracts and prints flat through sorting, transit and delivery.
• Prompt careful handling - many board-backed envelopes are pre-printed with 'Please do not bend', so couriers and post-room staff treat them with extra care.
• Speed up despatch - peel-and-seal closures let you pack and seal cardboard envelopes quickly without tape, keeping high-volume post rooms moving.
• Choose the right size every time - board-backed and cardboard envelopes are stocked in popular A4, A5 and standard document formats, with capacity mailers for thicker items.
• Present your brand professionally - clean white and neutral brown finishes give a tidy, consistent exterior for client-facing and premium document mailings.
• Support your sustainability goals - much of the range is recyclable and made from recycled board, helping you cut packaging waste with kerbside-recyclable materials.
• Secure confidential contents - tamper-evident locking formats show clear signs of interference for sensitive or high-value paperwork.

Choosing the right cardboard envelope:

When selecting cardboard backed envelopes and mailers, consider:

• Contents and rigidity needed - flat paperwork such as certificates and contracts suits a board-backed do not bend envelope. Thicker items like books and catalogues need a rigid or capacity mailer.
• Size and format - measure your document flat and match it to a standard A4, A5 or C4 format. Allow a little clearance so contents slide in without forcing the seams.
• Closure type - peel-and-seal strips speed up high-volume despatch; locking or tamper-evident flaps suit confidential or valuable contents.
• Presentation - white cardboard envelopes give a cleaner, more premium look for client-facing post; brown board is the cost-effective choice for internal and everyday mailings.
• Sustainability - if kerbside recyclability matters to you or your customers, choose recyclable board.

Examples include:

• Board-backed envelopes are ideal for posting single certificates, contracts and A4 documents flat.
• Rigid cardboard mailers protect books, magazines and prints that must not be folded.
• Capacity mailers suit thicker booklets, catalogues, books, games and phones.
• Tamper-evident envelopes secure confidential HR, legal and finance paperwork.
• If your items need cushioning rather than rigidity, our Jiffy bags or mailing bags are the right choices.
• For rolled posters and artwork, our postal tubes offer stronger protection; for everyday letters, standard business envelopes are more economical.

FAQs

What is a cardboard envelope?

A cardboard envelope is a postal envelope with a rigid board or card backing that keeps flat contents from bending or creasing in the post. Hard back envelopes and card backed envelopes are widely used for certificates, contracts, photographs, and A4 or A5 documents, and some are pre-printed with 'Please do not bend'.

What are 'do not bend' envelopes?

Do not bend envelopes are board-backed or all-board cardboard envelopes stiff enough to keep documents flat. They’re printed with a 'Please do not bend' message to prompt careful handling by couriers and postal staff. They’re the standard choice for mailing certificates, artwork and important paperwork that must arrive uncreased.

What is the difference between a card-backed envelope and a rigid cardboard mailer?

A card-backed envelope has one rigid board face with a paper or card front, keeping flat paperwork stiff and protected. A rigid cardboard mailer uses board for stronger all-round protection and is better suited to books, magazines and prints. Choose card-backed for single documents and rigid mailers for thicker or heavier flat items.

What size cardboard envelopes do I need?

Measure your document flat at its widest and longest points and choose the next size up, allowing a little clearance so contents slide in without stressing the seams. RAJAPACK stocks board-backed and cardboard envelopes in popular A4, A5 and C4 document formats, plus capacity mailers for thicker items. Contact the RAJAPACK team if you need help matching a size.

Are cardboard envelopes recyclable?

Most cardboard and board backed envelopes are widely recyclable with paper and cardboard at kerbside, and a large part of the RAJAPACK range is made from recycled board. Check for any non-paper elements such as plastic windows or bubble linings, which may need separating before recycling.

Can I send books and DVDs in cardboard mailers?

Yes. cardboard mailers and capacity mailers are designed for books, magazines, DVDs and prints, protecting them from bending and corner damage in transit. For thicker or multi-item orders, choose a capacity or expandable alternative that gives extra depth without forcing the contents.

Protect every document in the post with RAJAPACK UK

From board back envelopes and do not bend envelopes to rigid and capacity mailers, RAJAPACK UK supplies durable, recyclable cardboard envelopes that keep your documents flat, secure and professionally presented. With a wide choice of sizes, finishes and closures, plus next-day UK delivery and bulk discounts, it's easy to keep your post room stocked. Our packaging experts can recommend the right combination of cardboard envelopes and mailers for your documents and despatch volumes. Contact our team of packaging experts for advice.