This is caused by the mail client not being configured correctly. In Outlook:

1. Click on Tools
2. Click on Email Accounts
3. Ensure View or change existing email accounts is checked
4. Click Next
5. Highlight your email account, for example abc@mywebsitename.com
6. Click Change
7. Click on More Settings button
8. Click on Outgoing Server tab
9. Ensure the box next to the My outgoing server (SMTP) requires authentication is checked.
   • If it is not checked, then click in the box to cause a check to appear.
10. Click OK
11. Click Next.

Repeat the above steps if you have more than one email account, or Click finish