Why is my message not sent when I received a 200 response from send API call?

When a POST /send request is successful, you'll receive an HTTP status code 200 response. 

This DOES NOT mean that the message was received by the recipient.

What does this mean? 

  • When we send a message to the sender's SMTP server, the SMTP server sends us confirmation that the message was received for processing. Once we receive confirmation, the API returns the 200 response.
  • A 200 HTTP status code means that we have delivered the request to the provider. Now it's up to the provider to send it forward. In the case of sending a message, this means that there is no real way to know if the message has been delivered or not except for open tracking.
  • If the message isn't delivered, it is up to the provider to send back a bounced message or not. If you receive a bounce message, it typically is in the same thread as the original sent message but not required to be (See Why are bounce replies or non-delivery reports (NDRs) not available?). If a bounced message isn't received, please ask the end user to contact their email administrator. 



All about sending and bounce detection
Sent email not received



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