SES.sendRawEmail Only Uses The First Attachment In Gmail (Nodejs) - email

Question

I am trying to send an email with multiple attachments using AWS SES and nodejs.
My js script calls ses.sendRawEmail like so:
const params = {
RawMessage: {
Data: rawMailBody
},
Destinations: [],
Source: 'testemail#gmail.com'
};
ses.sendRawEmail(params, function (err, data) {
if (err) console.log("Error: " + err);
else {
// console.log("Success call: ", JSON.stringify(data));
console.log("Success.");
return data
}
});
This is how I am creating the "rawMailBody" object:
const BUCKET = 'my-bucket';
var rawMailBody = "From: testemail#gmail.com\n";
rawMailBody = rawMailBody + "To: testemail#gmail.com\n";
rawMailBody = rawMailBody + "Subject: Test Subject\n";
rawMailBody = rawMailBody + ``
rawMailBody = rawMailBody + "MIME-Version: 1.0\n";
rawMailBody = rawMailBody + "Content-Type: multipart/mixed; boundary=\"NextPart\"\n\n";
rawMailBody = rawMailBody + "--NextPart\n";
rawMailBody = rawMailBody + "Content-Type: text/html; charset=iso-8859-1\n";
rawMailBody = rawMailBody + "\n";
rawMailBody = rawMailBody + htmlData;
rawMailBody = rawMailBody + "--NextPart\n";
console.log('attaching attachments')
const attachmentFilename = 'Evaluates2-Old-Logo.pdf';
const attachmentFilename2 = '2019-W-4.pdf';
console.log('adding attachment', attachmentFilename)
rawMailBody = rawMailBody + "Content-Type: application/octet-stream\n";
rawMailBody = rawMailBody + "Content-ID: random1565323918273545letters\n";
rawMailBody = rawMailBody + 'Content-Disposition: attachment; name="Evaluates2-Old-Logo.pdf"; filename="Evaluates2-Old-Logo.pdf";\n';
rawMailBody = rawMailBody + "Content-Transfer-Encoding: base64\n";
rawMailBody = rawMailBody + await getImgDataBuffer('Evaluates2-Old-Logo.pdf', BUCKET); + "\n\n";
rawMailBody = rawMailBody + "--NextPart\n";
console.log('adding attachment', attachmentFilename2)
rawMailBody = rawMailBody + "Content-Type: application/octet-stream\n";
rawMailBody = rawMailBody + "Content-ID: random1565323443423794letters\n";
rawMailBody = rawMailBody + "Content-Transfer-Encoding: base64\n";
rawMailBody = rawMailBody + 'Content-Disposition: attachment; name="2019-W-4.pdf"; filename="2019-W-4.pdf";\n';
// rawMailBody = rawMailBody + "Content-ID random3965323447923784letters\n";
rawMailBody = rawMailBody + await getImgDataBuffer('2019-W-4.pdf', BUCKET); + "\n\n";
rawMailBody = rawMailBody + "--NextPart\n";
rawMailBody = rawMailBody + "--NextPart--\n";
I am getting the image data base64 buffer like this:
const getImgDataBuffer = (imageFilename, bucket) => {
return new Promise((resolve, reject) => {
var params = { Bucket: bucket, Key: imageFilename };
s3.getObject(params, function (err, data) {
if (err) {
console.log(err, err.stack); // an error occurred
reject(err)
}
else {
console.log(data.ContentLength);
console.log(data.ContentType);
console.log(data.Body);
console.log('got ', imageFilename)
resolve(data.Body.toString('base64'))
}
})
})
}
I am getting very strange behavior in gmail- it only takes the first pdf I send. The first pdf comes through perfectly, but the second doesn't come through at all. When I swap the order that the attachments are added to the rawMailBody object it still renders only the first one.
When I choose "show original" in gmail I can see that the entire MIME block for the second attachment is completely missing...
Is this expected behavior for gmail to remove subsequent attachments after the first one? Am I just doing it wrong?
Thanks!