Your email service provider, or ESP, is just the tool you use to send out all your emails and keep track of your list, like the post office for your messages. Picking a good one matters because it affects how many of your emails actually land in the main inbox instead of the spam folder. A good ESP also gives you the tools to easily set up automatic emails and see good reports on who opened what. If the tool is hard to use, it will slow down everything you try to do with your marketing. When thinking about an ESP, is making sure it has good delivery rates more important than having lots of fancy features?