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

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

This DO NOT mean that the message is received by the recipient.

What does this mean?

When we send a message to the sender's SMTP server, it sends us a confirmation that it received the message and will process it further. That's when we send the 200 response back.
A 200 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 should be in the same thread as the original sent message. If a bounced message isn't received, the user would have to reach out to their email admin.

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Updated March 15, 2023 00:40