Mailchimp is an email marketing platform that makes creating, sending and analyzing your email campaigns attainable for non-technical users. For the advanced users, they have powerful customizations and integrations that are integral for mature email marketing.
Honestly, after having used Mailchimp for nearly a decade, we don't often look at other email marketing platforms. There are a few top dogs in the email game, and Mailchimp definitely deserves a spot on that short list. We know a few email enthusiasts whose whole world is email (looking at you Mailcharts) — but unless you have really niche needs, Mailchimp is probably a great option.
Mailchimp is a low friction way to get your email marketing up and running. For 90% of small business, Mailchimp will work great. They are a great company with a solid tool.
My two qualms with Mailchimp: