We suggest to leave it since the warning only appears when you restart your Outlook and send out email.
If you want to disable it, there are 2 ways.
Solution 1
Turning off the SSL encryption requirement. This however may leave your correspondence vulnerable.
- Open Outlook
- Click ‘Tools’ from the top menu
- Select ‘account settings’ from the ‘tools’ menu
- Highlight the email account you are having trouble with and press ‘Change’
- From the ‘Change e-mail account’ page click on ‘More settings’
- From the ‘Internet email settings’ page choose the ‘advanced’ tab
- Un-tick the ‘This server requires authentication’ option
- click ‘OK’, then ‘next’ then ‘Finish’
Solution 2
Turn off e-mail matching for certificates in Outlook by modify the registry (Warning: Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. We advise not to use this method unless you are train to do so.
Please see microsoft website for more instructions by click on here.