550-not permitted to relay through this server

The "550 not permitted to relay" error means the mail server is rejecting your outgoing email because it does not recognize you as an authorized sender. This almost always comes down to incorrect SMTP authentication settings in your email client.

01. What "Not Permitted to Relay" Means

Email relaying is when a mail server accepts a message and forwards it to another server for delivery. Open relays (servers that relay email for anyone) are a massive spam vector, so mail servers are configured to only relay email for authenticated users.

When you send an email through our server, the server needs to verify that you have a valid account. It does this through SMTP authentication, where your email client sends your username and password before the server accepts the outgoing message. If authentication is not enabled in your client, the server sees an unauthenticated connection trying to send email and rejects it with "550 not permitted to relay."

02. Fix: Enable SMTP Authentication

In Microsoft Outlook

1. Go to File > Account Settings > Account Settings
2. Select your email account and click Change
3. Click "More Settings"
4. Go to the "Outgoing Server" tab
5. Check "My outgoing server (SMTP) requires authentication"
6. Select "Use same settings as my incoming mail server"
7. Click OK and then Next > Finish

For a complete Outlook setup guide, see How to Set Up Email in Microsoft Outlook.

In Apple Mail

1. Go to Mail > Settings > Accounts
2. Select your account and click "Server Settings"
3. Under "Outgoing Mail Server (SMTP)", make sure your username and password are filled in
4. Uncheck "Automatically manage connection settings" if you need to set the port manually

In Thunderbird

1. Go to Account Settings > Outgoing Server (SMTP)
2. Select your server and click Edit
3. Under "Security and Authentication", set Authentication to "Normal password"
4. Enter your email address as the username

In iPhone / iPad

1. Go to Settings > Mail > Accounts
2. Select your account > Account > SMTP
3. Tap the primary server
4. Make sure "Authentication" is set to "Password" and your username and password are filled in

See How to Set Up Email on Your iPhone or iPad for the full walkthrough.

03. Verify Your SMTP Settings

Even with authentication enabled, wrong settings will prevent sending. Here are the correct outgoing mail settings for Ultra Web Hosting:

• Outgoing server (SMTP): mail.yourdomain.com (replace with your actual domain)
• Port: 465 (SSL) or 587 (STARTTLS)
• Encryption: SSL/TLS (for port 465) or STARTTLS (for port 587)
• Authentication: Required (password)
• Username: Your full email address (e.g., you@yourdomain.com)
• Password: The password you set for this email account in cPanel

04. Other Causes

Sending from the wrong address

If your email client is configured to send "From" an address that does not exist on the server, the server will reject it. Make sure the "From" address in your account settings matches an email account you have actually created in cPanel. See How to Create Email Accounts and Aliases.

Sending from webmail works but desktop client does not

If you can send via Roundcube or Horde webmail but not from Outlook or Thunderbird, the problem is definitely in your desktop client's SMTP settings. Webmail uses the server directly and bypasses client configuration entirely.

Password recently changed

If you recently changed your email password in cPanel but did not update it in your email client, authentication will fail. Update the password in your client's account settings.

Quick Recap

1. The error means SMTP authentication is not enabled - The server rejects unauthenticated senders
2. Enable "My outgoing server requires authentication" in your email client
3. Use port 465 (SSL) or 587 (STARTTLS) - Avoid port 25
4. Username is your full email address - Not just the part before the @
5. Test with webmail first - If webmail works, the issue is in your client settings

Helping users fix email sending issues · Last updated March 2026 · Browse all Email articles