Unable to resolve Bad Request 400 sending email with Gmail Api and Service Account

Question

After following many responses to bad request 400 in this forum, I have run out of options to resolve the issue when sending emails via a service account and Gmail API & Oauth. Every solution I have tried doesn't seem to change the error so I am guessing I missing something higher up.

Steps:

followed Gmail api guides for code
Set up GCP and Google Admin ( followed this to start medium.com/lyfepedia/sending-emails-with-gmail-api-and-python-49474e32c81f)
specifically....set up the service account in Google Cloud Console for the project,
authorised for domain wide access,
added to the JSON credential file to the project.
authorised API clients with the Service Account ID in the admin console, provided every combination of scopes possible currently "Email (Read/Write/Send) https://mail.google.com/, https://www.googleapis.com/auth/gmail.send"

The GCP API dashboard shows requests are being made but with 100% errors.

The error returned in the app:

com.google.api.client.googleapis.json.GoogleJsonResponseException: 400 Bad 
Request
{
  "code" : 400,
  "errors" : [ {
    "domain" : "global",
    "message" : "Bad Request",
    "reason" : "failedPrecondition"
  } ],
  "message" : "Bad Request"
}

And my code

import android.content.Context;
import android.os.AsyncTask;
import android.widget.Toast;

import com.google.api.client.extensions.android.http.AndroidHttp;
import com.google.api.client.googleapis.auth.oauth2.GoogleCredential;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.google.api.client.util.Base64;
import com.google.api.services.gmail.Gmail;
import com.google.api.services.gmail.GmailScopes;
import com.google.api.services.gmail.model.Message;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Arrays;
import java.util.List;
import java.util.Properties;

import javax.mail.MessagingException;
import javax.mail.Session;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;

public class mod_gmail_send_2 extends AsyncTask<Void, Void, String> {

    private Gmail mGmailService = null;
    private GoogleCredential mCredential;
    private Context mContext;

    private String userID = "me";
    private String emailFrom = "xxxx@gmail.com"; //non specific  account?!?
    private String emailTo = "xxxxx@gmail.com";
    private String emailSubject = "This is the subject";
    private String emailBody = "This is the body text";
    private List<String> scopes = Arrays.asList(GmailScopes.GMAIL_SEND);

    public mod_gmail_send_2(Context myContext) {
        mContext = myContext;
    }

    @Override
    protected String doInBackground(Void... params) {

        try {
            mCredential = GoogleCredential
                    .fromStream(mContext.getResources().openRawResource(R.raw.myjsoncredentials))
                    .createScoped(scopes);
            HttpTransport transport = AndroidHttp.newCompatibleTransport();
            JsonFactory jsonFactory = JacksonFactory.getDefaultInstance();
            mGmailService = new Gmail.Builder(transport, jsonFactory, mCredential).build();
            MimeMessage mMimeMessage = createEmail(emailTo, emailFrom, emailSubject, emailBody);
            sendMessage(mGmailService, userID, mMimeMessage);

        }catch(Throwable e){
            return e.getLocalizedMessage();
        }
        return "Success";
    }

    public static Message sendMessage(Gmail service,String userId,MimeMessage emailContent) throws MessagingException, IOException {
        Message message = createMessageWithEmail(emailContent);
        message = service.users().messages().send(userId, message).execute();
        System.out.println("Message id: " + message.getId());
        System.out.println(message.toPrettyString());
        return message;
    }

    public static MimeMessage createEmail(String to,String from,String subject,String bodyText) throws MessagingException {
        Properties props = new Properties();
        Session session = Session.getDefaultInstance(props, null);
        MimeMessage email = new MimeMessage(session);
        email.setFrom(new InternetAddress(from));
        email.addRecipient(javax.mail.Message.RecipientType.TO,new InternetAddress(to));
        email.setSubject(subject);
        email.setText(bodyText);
        return email;
    }

    public static Message createMessageWithEmail(MimeMessage emailContent) throws MessagingException, IOException {
        ByteArrayOutputStream buffer = new ByteArrayOutputStream();
        emailContent.writeTo(buffer);
        byte[] bytes = buffer.toByteArray();
        String encodedEmail = Base64.encodeBase64URLSafeString(bytes);
        Message message = new Message();
        message.setRaw(encodedEmail);
        return message;
    }

    @Override
    protected void onPostExecute(String output) {
        Toast.makeText(mContext, output, Toast.LENGTH_LONG).show();
    }
}

Any ideas would be appreciated!!

plam · Answer 1 · 2019-02-03T23:42:43.987

It appears (and I stand to be corrected, or should I say wish to be corrected) that you cannot send an email from a service account. You must instead impersonate an account registered in your gsuite domain and include it when creating your google credential with .createDelegate().

 GoogleCredential
    .fromStream(service_account_json_credentials)
    .createDelegate(your_impersonated_account@your_domain)
    .createScoped(scopes)

See https://stackoverflow.com/a/54108538/9175763

Whilst you can share drive folder/files to your service account for access using the Drive API, you cannot delegate a private Gmail to your service account. "Error: Google account address you have specified is invalid."

You can however use a g-suite email alias as the delegate from your existing g-suite email. Simply add the alias to the user in the Admin console then open your g-suite email account as normal, go to settings, accounts, send mail as and add your alias. You can then set the delegate to your alias.

Unable to resolve Bad Request 400 sending email with Gmail Api and Service Account

1 Answers1