Check your SMTP configuration, verify the email content for errors, and ensure your application is handling exceptions properly.

Troubleshooting problems with email sending in your Node.js application is crucial for maintaining communication with users and ensuring functionality. Start by checking your SMTP configuration to ensure that the server, port, username, and password are all correct. If you’re using an email sending service like SendGrid or Mailgun, verify that your API keys or credentials are set correctly and have the necessary permissions. Next, review the email content being sent; ensure there are no issues such as missing fields or malformed HTML that might cause the email to be rejected or filtered as spam. Implement error handling in your email-sending logic to capture and log any errors returned by the SMTP server or email service. Monitor your application logs for any messages that indicate what might be going wrong; these logs can provide valuable insights into whether the issue lies with the application code or the email provider. Additionally, consider testing your email functionality in a local or staging environment to rule out configuration issues. If you suspect that emails are being marked as spam, review the sender's reputation and ensure compliance with email best practices to improve deliverability. By systematically addressing these aspects, you can effectively troubleshoot and resolve issues related to email sending in your Node.js application.