Mail that won't send usually fails at one of four points: the app's outgoing settings, the password, the connection, or a server-side limit. Work through these in order and you'll find the problem quickly.
1. Read the actual error
When a send fails, your mail app shows a message. Copy it down — it's the fastest clue. The most useful errors:
| Error | Meaning |
|---|---|
| Authentication failed / 535 | Wrong username or password for the SMTP server |
| Connection timed out / cannot connect | Wrong server address or port, or a firewall |
| Relay access denied / 550 | The app is trying to relay through a server it shouldn't |
| Quota exceeded / 552 | Mailbox or sending limit reached |
2. Verify the outgoing settings
Compare your app's outgoing (SMTP) settings with the reference table:
- Server: mail.yourdomain.com (or the hostname in your welcome email).
- Port: 465 with SSL, or 587 with TLS. Many apps default to port 25, which is blocked for security on most networks and fails immediately.
- Authentication: must be enabled, using the full email address as the username.
3. Reset the password in cPanel
If you get an authentication error, log into cPanel, open the mailbox, and set a fresh password. Update it in your mail app and retry. If you recently rotated a password elsewhere and forgot to update the app, that's exactly the cause.
4. Check sending limits and disk space
WebFulHost enforces sensible limits on how much mail an account can send per hour, to keep spam from ever being sent from our network. Repeated bulk sends trip the limit and mail stops until the window resets. Check the mailbox quota too — a full mailbox can reject new mail. See Email Not Receiving for where quota sits in cPanel.
5. Try webmail
As a quick cross-check, log into webmail in your browser and send a test message from there. If webmail sends fine, the problem is your desktop or phone app's settings. If webmail also fails, the issue is server-side — submit a support ticket and paste the exact error message.