AWS SES emails always go to Spam even after verification - email

Question

I am sure many asked the same question but I can't find an answer that is comprehensive.
We are running a web app (myapp.com) on an EC2 instance deployed on the Sydney region. The app sends emails via AWS SES. Because SES is not available in Sydney, we have configured SES in Oregon. We generated the SMTP credentials and configured our Springboot application to send emails using these credentials. We are able to send the email and the email gets delivered successfully but it goes to the SPAM folder.
The email from address is: noreply#myapp.com
We have verified the domain name in the SES console
We have verified the noreply#myapp.com email address in the SES console
DKIM is also turned on and verified
However,
We are not sure why the email keep getting delivered to the SPAM folder.
When I viewed the RAW email message I can see the SPF header:
SPF: NEUTRAL with IP xx.xx.xx.xxx
I haven't configured any SPF record in my DNS name but as I understand it I don't need to because I am using SES SMTP server and not custom MAIL FROM.
I am at lost as to why the email is getting delivered to SPAM.
Can any one help?

Answer 1

Solved the issue.
I am not sure exactly what was happening, but when using the SpringBoot JavaMailSenderImpl to send emails using AWS SES, all emails were not being signed using DKIM (no DKIM headers on the outgoing email messages). This was causing some SMTP servers to treat our emails as SPAM.
I have resolved the issue by using Java Mail API (javax.mail) to send emails and once I've done that then all email messages are delivered with DKIM header and non of them went to the SPAM folder (tested against Gmail and Outlook).
Again, I am not sure why using SpringBoot JavaMailSenderImpl was causing the issue. My understanding is that the JavaMailSenderImpl uses Java Mail behind the scene but for some reason non of the emails contained the DKIM header.
Below is my email sender using Java Mail if it's going to help anyone out there.
try {
Properties properties = new Properties();
// get property to indicate if SMTP server needs authentication
boolean authRequired = true;
properties.put("mail.smtp.auth", authRequired);
properties.put("mail.smtp.host", "ses smtp hostname");
properties.put("mail.smtp.port", 25);
properties.put("mail.smtp.connectiontimeout", 10000);
properties.put("mail.smtp.timeout", 10000);
properties.put("mail.smtp.starttls.enable", false);
properties.put("mail.smtp.starttls.required", false);
Session session;
if (authRequired) {
session = Session.getInstance(properties, new javax.mail.Authenticator() {
protected PasswordAuthentication getPasswordAuthentication() {
return new PasswordAuthentication("ses_username","ses_password");
}
});
} else {
session = Session.getDefaultInstance(properties);
}
Message message = new MimeMessage(session);
message.setFrom(new InternetAddress("from#example.com"));
message.setRecipients(Message.RecipientType.TO, InternetAddress.parse("to#example.com"));
message.setSubject("This is a test subject");
Multipart multipart = new MimeMultipart();
BodyPart htmlPart = new MimeBodyPart();
htmlPart.setContent("This is test content", "text/html");
htmlPart.setDisposition(BodyPart.INLINE);
multipart.addBodyPart(htmlPart);
message.setContent(multipart);
Transport.send(message);
} catch (Exception e) {
//deal with errors
}