Install a program for mass mailing

I have to send 10,000 emails to clients 3 times a week. To do this, I need to install something so that I only change the text of the message and press the send button. Make it very quick and simple. Mailings via mail ru do not offer, there you can send only 30 letters every hour, and then everything is blocked anyway. I know there is a program like this on Google. I'm waiting for suggestions. The organization is a startup, there is no big money.