Outlook Error: 0x800CC79

Here’s a clear, professional response you can use to explain the “550 Relaying Denied” SMTP error and how to fix it:

Email Sending Error: 550 Relaying Denied

You may receive the following error message when attempting to send an email:

The message could not be sent because one of the recipients was rejected by the server.
Server Response: ‘550 … Relaying Denied’
Error Number: 0x800CCC79

The Cause of the Problem

This error typically means your email client is not using SMTP Authentication, which is required by all SMTP servers on the IndicHosts.net network in order to send email. Without authentication, the mail server will reject the outgoing message as a protection against spam and misuse.

Solution: Enable SMTP Authentication

To resolve this issue:

For Outlook (All Versions)

1. Open Account Settings in Outlook.

2. Select your email account and click Change.

3. Click More Settings.

4. Go to the Outgoing Server tab.

5. Check the box that says:

   ✅ “My outgoing server (SMTP) requires authentication”

6. Ensure the option “Use same settings as my incoming mail server” is selected.

7. Save and restart Outlook.

For Other Email Clients (Thunderbird, Apple Mail, etc.):

Enable SMTP authentication in the outgoing mail server settings. Use your full email address and password for authentication.

Additional Note: ISP Blocking Port 25

Some Internet Service Providers (especially in the U.S.) block Port 25 to reduce spam. If your emails are still failing to send after enabling SMTP authentication:

• Switch to an alternate port, such as 587 or 465 (with SSL) in your email client’s SMTP settings.

• Use your ISP’s SMTP server if required.

Summary

✅ Enable SMTP authentication in your email client.

🔄 Try alternate ports (587 or 465) if port 25 is blocked.

📧 Use your ISP’s SMTP server if required.

Once these settings are updated, your emails should be sent without errors.