“In addition, free services have to make money, too. They do so by including advertising inside your email messages. Some promote their own services, but others will place paid ads in the footer or at the end of your message. Such ad placements can distract subscribers from focusing on your message.”
Any free email marketing software comes with a hidden price. Many of them will include native advertising within your subscriber emails, which can be terribly distracting to your readers and may not make it through SPAM filters. Is a free service worth losing subscribers?