My PAID App Engine is restricting me to sending only 100 mails. I could not find any documentation to increase that limit.
Additionally it says there is 0.00/100 $ charge for mails exceeding 100 mails. I could not find any information on the billing documentation either - in terms of how to send mails beyond 100 and get charged for it/etc..
Any help is welcomed..
Google doesn't appear to be interested in directly offering the email sending service, so the quota is really small nowadays. Instead they have partners for this service, which you'd have to use if you need to exceed the quotas.
From Quotas and limits:
The quota is reset daily. If you exceed the daily quota, you will get an over quota exception. If you need to send more mail then the quota allows, you can use a third-party mail provider, such as SendGrid or Mailgun.
In addition to Mailgun and SendGrid, Mailjet is also a mail sending partner.
来源：https://stackoverflow.com/questions/45122113/gae-increase-recipients-emailed-limit