I am facing a problem that when i send to multiple recipients (about 100), it response forbidden. But it was fine previously. And I have tested to send few recipients (about 3), it works fine.
May i know is that any change on free plan? Many Thanks for the help.
The free Sendgrid plan allows you to send up to 100 emails a day. If you are trying to send more than that 100th email in a day then you won't be able to and you should upgrade to a plan that supports more emails.