This error occurs when a user or mail client attempts to send email without authenticating on the mail server. If this error occurs please follow the below options to resolve the issue you are experiencing.
1. Outlook 2000
Go to Tools > Services (or Tools > Accounts, if Services is not listed). Select your Internet E-Mail Account and press “Properties.” Go to the “Servers” tab, and check “My server requires authentication” under Outgoing Mail Server. Press “Settings,” select “Use same settings as my incoming mail server,” then press “OK” three times to save the changes & return to Outlook. Finally, restart your computer.2. Outlook 2002 & 2003
Go to Tools > E-Mail Accounts. Select “View or change existing e-mail accounts” and press “Next.” Select your Mail POP/SMTP account and press “Change.” Press “More Settings.” Go to the “Outgoing Server” tab, and check “My outgoing server (SMTP) requires authentication.” Select “Use same settings as my incoming mail server” and press “OK.” Press “Next,” then press “Finish” to confirm your changes and return to Outlook. Finally, restart your computer.3. Outlook 2007, 2010 & 2012
Go to Tools > Accounts Settings. Select "Email". Select your IMAP/POP/SMTP account and press “Change.” Press “More Settings.” Go to the “Outgoing Server” tab, and check “My outgoing server (SMTP) requires authentication.” Select “Use same settings as my incoming mail server” and press “OK.” Press “Next,” then press “Finish” to confirm your changes and return to Outlook. Finally, restart your computer.4. Outlook Express
Go to Tools > Accounts. Select the “Mail” tab. Select your Mail account and press “Properties.” Go to the “Servers” tab, and check “My server requires authentication” under Outgoing Mail Server. Press “Settings,” select “Use same settings as my incoming mail server,” then press “OK” twice times to save the changes, then press “Close” to return to Outlook Express. Finally, restart your computer.
