Trouble sending email with Gmail REST API - receiving error message

[olivias]

I’m encountering difficulties with the Gmail REST API when trying to send an email. Upon making the API request, I get a successful response (200 OK) along with a message ID, but the email fails to send.

Here’s the structure of my API request:

{
  "raw": "dGVzdGluZyBlbWFpbCBzZW5kaW5nIHdpdGggR21haWwgQVBJ",
  "payload": {
    "headers": [
      { "name": "to", "value": "[email protected]" },
      { "name": "from", "value": "[email protected]" },
      { "name": "subject", "value": "API Test Email" }
    ],
    "mimeType": "text/plain"
  }
}

The API returns what seems to be a valid response:

{
  "id": "148abc123def456g",
  "threadId": "148abc123def456g"
}

However, instead of delivering the email, I receive an error notification from [email protected] indicating that the message couldn’t be sent.

Has anyone faced a similar issue? What might be the reason for the API accepting the request while failing to send the email?

[HappyDancer99]

Had the exact same headache last year with Gmail API in our notification system. Your problem’s in the request structure - you can’t mix raw and payload fields. Gmail processes the raw field and ditches your payload headers, so your base64 string “dGVzdGluZyBlbWFpbCBzZW5kaW5nIHdpdGggR21haWwgQVBJ” becomes just body text with no email headers. Build the complete email message with all headers (To, From, Subject, Content-Type) as one string, then base64url encode the whole thing. Payload’s for different Gmail API endpoints, not the send method. Double-check your auth scope has gmail.send permission too.

[SparklingGem]

ur raw message encoding’s probably messed up. Gmail’s API is super picky about base64 format - encode the whole email (headers and all) as one raw string instead of splitting raw and payload. Also make sure ur OAuth scopes include gmail.send permission.

[Ethan99]

I hit this exact issue about six months ago while setting up Gmail API for our client portal. You’re mixing two different approaches here - the raw field needs the entire RFC 2822 message encoded in base64url, while the payload structure is for different API methods. When you include both, the API accepts it but Gmail’s backend gets confused. Ditch the payload object completely. Build your raw message with all headers and body content, then encode the whole thing. Also double-check that your auth token hasn’t expired and make sure the sender email matches your authenticated account.