SendGrid Multiple Emails to Multiple Recipients Node JS from Firebase Firestore - node.js

Question

I am using SendGrid and Firebase Functions to send multiple emails to multiple recipients. The code that I am using works correctly when sending to a test list of 4 email addresses, but does not work when trying to send to 4,000 email addresses. There is also no error message from SendGrid.
This code also works and returns the list of email addresses printed in the console if the SendGrid block of code is commented out.
Do you know what could be going wrong?
Thank you
exports.adminSendGroupMessage = functions.region('europe-west2').https.onCall((data, context) => {
const emailHTMLData = emailHTMLData;
var emailDataArray = [];
//Fetch contacts list
let testContactsRef = db.collection('contacts-list');
return testContactsRef.get().then(snapshot => {
snapshot.forEach(doc => {
// console.log(doc.id, '=>', doc.data());
console.log("Fetched contact with ID: " + doc.id);
//Extract contact data
const firstName = doc.data().name || "";
const surname = doc.data().surname || "";
const emailAddress = doc.data().emailAddress;
var emailData = {
to: emailAddress,
from: 'fromEmail#email.com',
subject: messageSubject,
text: 'Email for ' + firstName,
html: emailHTMLData,
customArgs: {
ref: 'msg-ref'
},
}
//Add new email data to the array
emailDataArray.push(emailData);
});
return Promise.all(emailDataArray).then(results => {
//Send emails with all data once contact fetch complete
console.log("Success fetching contacts - send emails.");
sendGridGroupMessages(emailDataArray);
return { success : true, message: "Success sending emails" };
})
});
function sendGridGroupMessages(emailDataArray) {
console.log('Send emails to group function with data: ' + emailDataArray.length);
var i,j, splitArray,chunk = 998;
for (i=0,j=emailDataArray.length; i<j; i+=chunk) {
splitArray = emailDataArray.slice(i,i+chunk);
// do whatever
//Send emails
sgMail.send(splitArray, (error, result) => {
if (error) {
//Do something with the error
console.log("Error sending group emails: " + error);
// throw new functions.https.HttpsError('internal', 'There was an error sending the group emails - ' + error.message + ' (' + error.code + ')');
} else {
//Celebrate
console.log("Success sending group emials: " + JSON.stringify(result));
// return { success : true };
}
});
}

Answer 1

You must post the error log
If no errors it means they sent
but check SendGrid activities to see what happened to these emails