Email is cheap, fast and efficient
Email is seriously cheap and although you should spend time in carefully crafting your copy (and feature it within a sales focused email design) it still makes for a great form of marketing with one of the best ROIs out there.
Email is marvellous for data analysis
Not only can your message be delivered immediately, you also benefit from results that are fully analysable through email campaign management software (perfect for honing future campaigns). Data
feedback can include bounce, open and click through rates, to name but a few.