One of the great things email has going for it is that it can adapt on a dime and turn on a penny, meaning that it has the potential always to be relevant and timely. This is very different from social media posts, which are less intensively targeted, less time-focused, and work on more of a broadcast basis. The capacity to intensively segment, target, and stream your email marketing also helps you to narrow your analysis to certain points. By doing this, you can learn a lot about your brand, your customers, and your marketing profile in general.
When you're using email as a marketing tool, you're working on a pretty personal basis. This isn't ‘drive-by' stuff -you're directly targeting customers from their inboxes. There's a huge amount of potential which comes with this kind of marketing... but you'll only reap that potential if you REALLY understand both the marketplace you're operating from, and the audience you're talking to.