I've been managing communities for the past 5 years and have used many tools. They all have pros and cons in my opinion.
- Mailchimp: If you're starting out, you can't go wrong with this one. There's a free tier and it grows with you.
- Sendgrid: Very reliable and easy and similar to mailchimp. I'm not super sure about their automated systems though.
- Bronto: If you want to get a bit more sophisticated (e.g. run an a/b test with your welcome series to have people go down a different path) but you don't want to spend a ton, Bronto isn't too bad.
- Mailgun: If you have a developer and want to automatically send emails and spend as little as possible, I really like Mailgun. Send them an API call with all your email content in it, and you're good to go. It's the cheapest but you'll need a developer or you'll have to write the code to deploy it. But, it's really great for automated weekly/monthly newsletters
- Responsys/ExactTarget/Cheetah: These are your enterprise level programs. Happy to talk about them if you need, but unless you're managing over 1MM in emails, stick with a lower price option.