How do I fix SMTP authentication?

Fix SMTP Server error in Email

1. Open your email client program (Outlook Express, Outlook, Eudora or Windows Mail)
2. Click "Accounts" in the "Tools" menu.
3. Click on your email account then click "Properties" button.
4. Click "General" tab.
5. Ensure that the "E-mail address" is your valid address for this account.
6. Click "Servers" tab.