If you find your Twilio SendGrid account is suddenly unable to send mail after the first week of the month, your account could be in a billing frozen state. This frozen state occurs when we attempt to process your payment, but the card on file for your account gets declined.
To reactivate your account, please update your credit card on file by logging into the Twilio SendGrid UI and going to the Billing tab on your Account Details page. Update your card information and then click Save. Once you update the card on file, the payment processes automatically, and your account is unfrozen.
Mail Requests During Frozen State
While the account is in a Billing Frozen state SendGrid will not honor requests to send mail. When we receive the request, it will go in to a processing status, but will ultimately be dropped by our server since the account is in an inactive state. Once the account is reactivated you may see messages that do not move from a "Processing" Status in your activity feed if any requests to send mail occurred while the account was in a frozen state:
Since the messages were ultimately dropped they will need to be re-triggered from your integration. SendGrid does not retain the content of these messages and will be unable to retry them automatically.