You can cancel your subscription anytime. Just open the add-on and go to your account. Here's a full guide on how to cancel your subscription.
Mailmeteor is fully managed from the Google Sheets add-on. Just open a spreadsheet, then select "Add-ons" in the menu, then "Mailmeteor > My Account" to manage your account.
If Gmail prompts this error after you've run a mail merge, it means that you've reached your sending capacity or that your email was detected as spam. Mailmeteor sends emails using your own Gmail account, this means that when your account reaches this limit, you can't send emails for a period of around 24 hours. Read this guide to learn more about how to fix this issue.
Mailmeteor uses anti-spam filters to keep the platform safe. In case you've been blocked you will receive a message like this "Sorry, you are temporarily blocked. Your activity on Mailmeteor has been reported as spam or misuse". Feel free to contact us if you think your activity is legit and we made a mistake.