Its mainly used for sending mass email campaigns. The free plan allows you to send campaigns upto 100 subscribers, which is okay. The deliverability of emails for my campaigns was higher when compared to the previous tool that I used.

Sendblaster customer service is through a chat feater/email because they're international, so I expected them to be slow to respond, but they weren't. They're responsive and they provide answers that work. Their platform is basic but very flexible for those who know enough programming/coding to be self sufficient. I know some basic HTML and was able to make Sendblaster work for monthly email sends to about 60,000 people work for several years (we later upgraded to Marketo).