https://chromewebstore.google.com/detail/mailflame-for-gmail-merge/cjhphjkkhpodgjambmhgginblammkhko?hl=en
Mailflame for Gmail: Merge, Send, Followup & Track emails - Chrome Web Store
Boost your email marketing with Mailflame. Easily send, schedule, and track email campaigns directly from Gmail.
for gmailmergesend