Hello, Kindly Look at the following I'm sure this really going to be very helpful for you 1. How is the email account configured in Outlook? 2. What is the email account type (POP3, IMAP or an Exchange)? 3. Did you make any changes to the Account Settings? 4. Is the Computer on network/domain? If you have setup POP3 or IMAP account, try disabling the option ‘This Server requires an encrypted connection (SSL)’ for the Outgoing server and check if this helps Open Outlook > Click on File > Account settings > Select the account and click on change > Click on More settings and click on Outgoing server tab > Check the box My Outgoing server requires authentication. Note: make a note of the settings before changing. Let me know the results to assist you further. If want to learn more briefly then, Look at this : the server you are connected to is using a security certificate that cannot be verified Thank you. ... View more