The world of promotional emails is changing as consumers become more leary of this type of email content. The world continues to grow in technology and available information, and consumers are being made more aware of when messages are overly promotional. The task then is to offer a good mix of engaging emails (how-to content, informational content, etc.) and promotions.
Make your promotional emails focus on the sell or offer, and highlight this focus using your stand-out CTA. Then, maybe beneath the main offer, you can provide additional free content that supplements the offer, using a less eye-grabbing CTA. This gives customers an on-ramp to dip their toes in without pulling the trigger on a purchase, which may give you more opportunity to convert them later on.