Delivery Error to Microsoft Domains

Based on the error message you're receiving, Microsoft is blocking emails from your IP address because it appears on their block list. This is a Microsoft-specific issue rather than an AWS problem.

When you receive a 550 5.7.1 error with the S3150 code from Microsoft domains (Hotmail, Outlook), it means Microsoft's filtering systems have identified your IP address as a source of problematic traffic. Even though you're using a managed dedicated IP and haven't intentionally violated any policies, there are several reasons this could occur:

The IP address may have a poor reputation due to previous usage by another customer, spam complaints from recipients, high bounce rates, or sending patterns that Microsoft's algorithms flag as suspicious. Sometimes legitimate senders get caught in these filters.

To resolve this issue, you should:

1. Contact Microsoft directly using the troubleshooting link provided in the error message (mail.live.com/mail/troubleshooting.aspx) to request delisting
2. Review your email sending practices to ensure you're following best practices (proper authentication, low complaint rates, engaged recipient lists)
3. Consider contacting AWS Support to discuss your dedicated IP's reputation and whether a new IP might be warranted
4. Ensure your SPF, DKIM, and DMARC records are properly configured

Microsoft maintains their own independent block lists and reputation systems, so even with AWS's managed infrastructure, you may need to work directly with Microsoft to resolve deliverability issues to their domains.