Troubleshooting (FAQ)

Q1: Authentication failed error (e.g., 535 5.7.8 Authentication credentials invalid)?

  • Check the username and password, and confirm whether an app-specific password is required.
  • Confirm that SMTP AUTH is enabled for the account. Corporate email systems or Exchange Online may disable this feature by default, requiring an administrator to enable it.

Q2: Connection timed out or unable to connect?

  • Check whether outbound traffic on ports 587/465 to the external network is blocked by a firewall or egress policy.
  • If using an internal relay, ensure that DNS can resolve its internal address.

Q3: Certificate verification error (e.g., tls: failed to verify certificate: x509: certificate is not valid for any names)?

  • This is usually caused by a mismatch between the hostname and the certificate's CN/SAN or an incomplete root certificate chain. Switch to a hostname that matches the certificate (such as the official domain specified in your provider's documentation) and ensure that the system trusts the root certificate.

Q4: Emails are rejected or sent to spam?

  • Confirm that SPF/DKIM (and optionally DMARC) are correctly configured and that the sender domain matches the From address.
  • Limit email volume initially and increase it gradually. Third-party providers (such as Mailgun) may also limit the sending rate.

Q5: I only want to receive Chinese (or English) alert emails. How do I set this up?

  • Set "Email Language" to cn (Chinese only) or en (English only). The system skips alert emails whose language does not match this setting.