This is without doubt the best plugin if you want to manage your newsletters inside WordPress. Easy to use, easy to explain to my customers.
For a lot of users the free version is enough, but if your audience increases, or you need the premium features, the pro version offers a cheaper and simpler option compared to other dedicated newsletter services.
And if your audience becomes huge, no problem: it’s possible to use external smtp sending services, or their integrated sending service, spending less than dedicated newsletter services, and having more control.
A must have plugin!