Envelope sizes in plain words
- DL — 110 × 220 mm. Fits a folded A4 letter; standard for business mail.
- C5 — 162 × 229 mm. Fits A4 folded once (A5); slightly more formal.
- C4 — 229 × 324 mm. Fits unfolded A4 and documents with rigid contents.
Pick by what you're putting inside; don't over-think it.
What mail merge really does
Mail merge takes a spreadsheet of addresses and produces one personalised envelope (or letter) per row. Done correctly you get 200 envelopes addressed to 200 different people without typing any of them. Done badly you get 200 envelopes printed with "Dear {FirstName}" literally. Always test with 3–5 sample records first.
Address positioning and OCR-friendly layout
Royal Mail reads addresses automatically. Keep the address block in the lower half of the envelope, at least 15 mm from any edge, with clear space around it. Use a plain sans-serif font at 10–12 point, left-aligned. Avoid italics, all caps and decorative fonts — they confuse sorting machines and delay mail.
Bringing us the file
Send the spreadsheet (CSV or Excel) with clean columns: Title, First Name, Last Name, Address 1, Address 2, Town, Postcode. We'll set up the merge, show you a proof, then print the whole batch. Budget 2–3 hours for first-time setup; same-day turnaround if the file is clean.
In short
We print DL, C5 and C4 envelopes with mail merge from your spreadsheet. Send a sample list to quote@copyshopputney.co.uk for a quote.
Published 15 April 2026 by the Copy Shop Putney team. Shop 395-A, Tildesley Rd, Putney Heath, London SW15 3BD.