The new system, which has reportedly caused confusion among customers already, means the price of postage will now be based on size as well as weight. Royal Mail claims the new system is fairer and that 80 per cent of all mail will cost the same or less to send.
Creativity can be a scary word and is sometimes seen as an indulgence.
But it's a powerful and sophisticated tool when used well - one that can help direct marketing packs achieve emotional engagement in a different way from the traditional sad images I see in too many items.
It seems almost certain that most charities and businesses will opt for a C5 envelope - which is suitable for a sheet of A4 folded in half - rather than for a C4, which holds an unfolded sheet of A4, because the former is cheaper.
For those charities that are successfully using C4 formats, the options are to continue and pay the extra levy or to explore C5 in a more creative way.
Raising income is on every charity's agenda. If you want to demand a higher price, in most markets you need to move your purchasing decision across the R&E (rational to emotional) line by adding emotional purchasing values. Just consider that the three things we tend to spend most on - holidays, homes and cars - are mainly emotional purchases.
With declining response rates, you have to work harder than ever to grab the attention of an audience suffering from charity fatigue. Data and research can only help you find the right people. To really grab their attention, stand out from the competition, create desire and get action, you need to be more imaginative.
When charities are creative they can be thought-provoking - they can shock you or even make you laugh or cry. I have been amazed at how humour works even when you are dealing with serious issues.
In charity marketing, however, creativity is more the exception than the rule. Most resort to safe, formulaic packs. The trouble is that the world is changing and the formulas don't work as well any more. It's time for change, to challenge traditional ideas and to be brave.
Maybe Royal Mail has effectively scored an own goal and will force charities to make greater use of the internet. Or perhaps in the future we may be thanking it for making charities challenge conventional thinking and think more creatively.
Chris Arnold is executive creative director of marketing agency Blac email@example.com
- For more information on pricing in proportion, visit the Royal Mail website, www.royalmail.com.