SMTP Connection Refused in Production for Cursor-Generated Email Code

Your Cursor-generated application sends emails perfectly during local development but fails with SMTP connection errors in production. Users aren't receiving signup confirmations, password resets, or notification emails. The server logs show connection refused, timeout, or authentication errors when attempting to connect to the mail server.

Email delivery is critical infrastructure — when it breaks, users can't sign up, can't reset passwords, and lose trust in your application. Cursor often generates SMTP code configured for a local mail server or development service like Mailtrap/Mailhog, which doesn't translate to production.

The issue might also manifest as emails being sent successfully according to your application logs, but never arriving in users' inboxes due to DNS, SPF, or deliverability configuration problems that only affect production domains.