Open and click-through rates (CTRs): Knowing who are engaged customers (those who open most emails and end up making purchases) versus inactive customers (who haven’t opened any emails in months) can be invaluable. Marketing campaigns announcing a new product should absolutely include those engaged customers, while re-engagement campaigns can be created to try and entice the inactive customers.
Be friendly. Feel free to use a casual tone in your email newsletters. Since most emails come directly from one person, people expect human voices in their inboxes. There's a good chance your subscribers are already in a informal frame of mind when they're checking their email, so an overly formal or stodgy voice might seem out of place. Plus, they've given you their email address, so you're already on a first-name basis. If you collect first names on your signup form, you can dynamically include them in your email greetings.
People buy when they feel that they have good reasons to do so. So, you need a strong value proposition (=great reasons for buying what you sell). If you don’t have it, you can’t be able to give people good reasons for buying. If you don’t know what—specifically—would make people see value in your offer, how could your email marketing (or any marketing) be effective?
Make your offers feel relevant. If you offer people something they don’t think is relevant for them, they also think you don’t know them or understand their situation. Segmenting people based on their interests, problems, company sizes, and other things can help with that a lot. But it’s not enough. Your offer might be a perfect fit for them, but how you present it has to be a fit, too. Focus on describing their problems, how they’ll use the product or service, and what they will have in the end. Don’t talk about it from your perspective. No one really cares what you think about your product as much as they care about what they’ll get from it.
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.