Envelopes
Envelopes can be reused by placing labels over the old address. Many charities provide reuse labels, so you can support a good cause at the same time. They can also be used as scrap paper.
Buy envelopes made from recycled paper. These can be bought from most stationery stores, many large supermarkets and charity shops.
Genuine cellophane window envelopes with real cellulose window film (which can be composted) are available from stationers nationwide.