Using multiple mail merges on same computer/IP(need help)

Hello guys. I would like to use multiple gmails and multiple licenses of gmass, yet another mail merge on same computer and ip. So i’m wondering if its safe? If its not safe to use on same ip and computer, then what program would you suggest to use?

Should i buy a separate proxy for each gmail/license or even VPN?

If i’m planning of sending emails from multiple gmails and multiple mail merges, what would be the best solution? Let me know please, thank you!