Connection or authentication fails

  1. Confirm host, port, SSL/STARTTLS combination, username, and provider SMTP access.
  2. For Gmail, use a valid App Password where supported.
  3. Check internet access, firewall, and network restrictions.
  4. Use the account's Test Connection or Verification tools → SMTP tester → Test Now. The standalone tester may use a live challenge test; follow its prompts.

A sent message does not arrive

Read the send result first. SMTP acceptance is not proof of inbox placement. Check recipient spelling, Spam/Junk, provider filtering and quotas. Account setup itself no longer requires a verification code.

Report safely

Record the app version, OS, host, port, security type, and redacted error. Never include passwords, license keys, or API keys. See support.

Check which authentication the provider accepts

Use the provider tutorials. Outlook.com requires OAuth2; a preset is not OAuth support. For managed Microsoft or Google mailboxes, check organization policy. Proton Bridge needs a local credential and trusted certificate. Do not disable TLS or certificate validation to get past a connection error.