The best alternatives to PostSheet are Polymail , Stamp Ready, and The Letter Sender. If these 3 options don't work for you, we've listed a few more alternatives below.
Polymail is the email platform for teams. By combining email with real time collaboration and integrating it with your team's other tools, Polymail allows everyone to work together seamlessly, move faster, and be more productive.
Daily Sender never restrict you like other services and offer you unlimited campaigns, auto-responsders, contact without any limit. Daily Sender is the best bulk email marketing service. You can send unlimited emails with one click.