I own Atomic Email Studio. Never tried SendBlaster.
Here's what you should do OP:
Sign up for Amazon SES on all 3 regions (Oregon, N.Virginia, and Ireland). Then confirm your domain and email with all 3 regions. Then ask them to lift your sending restriction. When they lift it, you'll be able to send around 50k emails per day from each region (150k total). Then add the SMTP to Atomic Email Studio.
AES works well for me. I'm doing high volume sending and I never have issues. Getting setup was a pain but now that it's running, the clients and money are rolling in.
Amazon SES lets you send 60,000 free emails per month in the free tier. That's more than most people send.
I could never deal with the limitations and low deliverability of free email providers. Do this right OP. Don't skimp on your email system. It will make you a lot of money in the long run.