Quotas for Google Services
Google spreadsheet is awesome and completely free tool.
But, it have some quotas on services.
Email recipients – its count how many emails app can send during 24 hours. Each google user can do 100 emails on free account, and 1500 emails on buisness account.
More about quotas
Get email recipients per day programmatically
function googleMailGetQuota() {
return MailApp.getRemainingDailyQuota();
}
var emails = googleMailGetQuota();