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 2007
Go to Tools > Account 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.

2. Outlook 2010 & 2013
Go to File > Account Settings > Account 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.

3. Outlook 2013, 2016 and 2019
Go to File > Account Settings > Manage Profiles > Email Accounts. 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.

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