Why are the emails that I send using Amazon SES getting marked as spam?

Amazon SES attempts to deliver email messages to the recipient's mail server (ISP) until the ISP accepts the message and sends a 250 OK response. If Amazon SES is unable to deliver your email, it returns an error message similar to the following:

"550 4.4.7 Message expired: unable to deliver in 840 minutes."

If the ISP accepts the email and sends a 250 OK response, then the ISP decides whether the email is categorized as spam and determines the overall mailbox placement. If the ISP flags the email message as spam, then the email might be placed in the recipient's spam or junk folder.

Often, ISPs have spam filters with rules that are set up by the ISP. These rules determine whether to process an email as spam or to drop the email entirely.

Several factors can lead to an ISP flagging an email as spam, such as:

• The email content and quality. For example, ISPs can use their own content filters that scan emails for specific keywords, insecure links, links considered harmful, or links to domains that aren't the sending domain. Emails that are considered low quality might be placed in the spam or junk folder, or even blocked by the ISP. Amazon SES requires that you send high-quality email.
• Lack of email authentication, such as DomainKeys Identified Mail (DKIM) or Sender Policy Framework (SPF)
• Sending domain or IP address reputation
• Multiple emails flagged as spam
• High bounce or complaint rates

To learn more about the best practices for sending emails with Amazon SES, see Tips and best practices.