What anyone preparing a marketing email needs to know is the difference between opinion and fact. You will want to entice customers into buying, or even just reading, the email by telling them just how good your product is. Lurking at the back of your mind will be the knowledge that one of the subscribers to your email marketing list might well feel misled if you go over the top and they might complain to the Advertising Standards Authority (ASA).
The website of the Committee of Advertising Practice states in effect that if you make a factual claim about your product, such as it being the most economical of its kind, then you must be able to prove this claim objectively. If you merely suggest that customers will be more satisfied with your product than they are with the one they are using now, then that is merely opinion.
Sweaty Betty, a company selling sports gear for women, had an advert in their catalogue for a pair of trainers made by a company which, via a dedicated scientific approach, to manufacture produced “some of the most comfortable and performance enhancing shoes on the market.” They had to either demonstrate that the words were merely fluff or prove their claims by some sort of evidence. They chose, in effect, to do both.
They were able to produce a group test by an independent magazine where their shoes were praised and were placed amongst the best. Or, to put it another way, were some of the most comfortable and performance enhancing . . . etc. In other words, they were not saying anything quantifiable. However, they went a bit further.
They suggested, and convincingly, that “performance enhancing” was a sort of generic phrase that referred to the wearer's performance and not that of the trainers. The ASA found for Sweaty Betty.
The message is quite clear. Choose your words carefully although there is no need to run scared. If your claim is precise, the fastest for instance, then ensure you have sufficient evidence to back your claim. If you say something a little less precise then you are in the clear.