If there’s one tool that I recommend above all other solutions it’s ActiveCampaign.

ActiveCampaign is the backbone of all of our ventures here at Venture Harbour. It’s easy to use, and easily the most feature-packed email marketing / marketing automation tool for small to medium-sized businesses. On top of that, it’s also one of the most affordable tools.

What sets ActiveCampaign apart is the fact that it has its own CRM system for managing leads, and marketing automation for nurturing your leads into customers. In short, it’s an all-in-one platform for handling small business sales and marketing. Unlike some of the other tools that do this, ActiveCampaign is affordable starting at $9/month – a twentieth of the starting cost of tools like Infusionsoft, Hubspot and Ontraport.

This depends on what do you want to achieve with email marketing. Depending on your budget, communication volume(current and estimated), features required, target audience, etc., there are different options. I will be happy to discuss this over a call with you.

If you are looking to do cold-email blasts to prospects a traditional provider like sales-push, mailchimp, or responsys is not going to get great click-through or response rates because people instinctively tune out and unsubscribe because it's spam.
A series of plain-text emails will be the best for this. Outreach.io ($100 / mo) or Yet Another Mail-merge (free Google Sheets plug-in) will be the best. Outreach.io is great because you can create email sequences and so much more, however.
I don't have all the details with regards to what you are looking to accomplish so it's hard to say. However, if you are getting people signing up for a list (via blog, paid ads, etc) then a mail list provider with marketing automation included is ideal. For starting out, most startups use Mailchimp because it's easy to set-up, has strong analytics, and includes Mailchimp automation (marketing automation) and Mandrill (transactional emails / basically competitor to Sendgrid).

Tools to use if you need mail-list / marketing automation:
High End
-responsys - most expensive but best
-epsilon
-exact target
-experian

Mid-tier
-Silver pop
-strong mail
-lyrics
-sail thru

SMB/Startup
-mailchimp - most startups use this to start and then switch later once it becomes less cost efficient
-vertical response
-icontact
-campaign monitor

I have actually written a blog post about this! Feel free to read this blog post that lists a bunch of different email software based on your monthly budget. I think the post will help answer a ton of questions and please let me know i you need more assistance or if you need help performing email marketing tasks or installing/setting up the software. http://www.bloominari.com/blog/email-software-choices-for-every-business-budget