Entice customers to sign up for your mailing list with discounts or exclusive offers. Include an image for extra impact.
https://www.ncbi.nlm.nih.gov/pubmed/17092697
https://www.ncbi.nlm.nih.gov/pubmed/27274631
https://aiche.onlinelibrary.wiley.com/doi/full/10.1002/aic.14220