Transactional emails (like an order confirmation) are best sent immediately after the purchase is made. Lifecycle emails—which are sent based on specific behaviors a customer exhibits—require a little more testing to get right. The best time to send an abandoned cart email, for example, can vary based on the reason for abandonment and your strategy for recovering those orders.
Next up is building an email newsletter. The best services offer several ways to do this; you can import your own HTML, start from scratch, or use a predesigned template. Most of these services have drag-and-drop UIs that let you choose exactly the elements you want to include, as well as image libraries in which you can store assets such as your logo or company photos. Tools that let you test your emails for spam are also essential since there are some seemingly innocuous terms that may send up red flags and drop all of your hard work into your subscribers' junk folders or, worse, get your emails banned before they ever reach their recipients.
The ideal type of opinion (unrelated to your expertise) is one that doesn’t offend anyone, but makes some people relate to you more. For example, I’m a vegetarian. I used to protest whenever there wasn’t a big piece of meat on my plate. But when I tried eating just veggies for a couple of months, I realized I felt a lot more energetic. Sure, it’s more ecological. And often animals are treated cruelly. But those aren’t the things I emphasize if someone asks why I’m a vegetarian. No one in their right mind has a strong negative reaction to someone eating food that makes them feel energetic, right? But for some vegetarians it’s a very meaningful choice, so it might have a positive impact on those people. That said, I highly doubt that my choice of diet have any direct impact on my sales.
Another type of electronic mailing list is a discussion list, in which any subscriber may post. On a discussion list, a subscriber uses the mailing list to send messages to all the other subscribers, who may answer in similar fashion. Thus, actual discussion and information exchanges can happen. Mailing lists of this type are usually topic-oriented (for example, politics, scientific discussion, health problems, joke contests), and the topic may range from extremely narrow to "whatever you think could interest us". In this they are similar to Usenet newsgroups, another form of discussion group that may have an aversion to off-topic messages.