When using Yahoo Mail, I get a message that says "No internet connection". My internet connection is fine,but I can't use Mail. How do I fix this repeating problem?

Do you have the Dashlane extension installed?

Try setting up another admin user account to see if the same problem continues. Also try the Safe Mode.

Safe Mode - About El Capitan
also Sierra

Safe Mode Startup – El Capitan. also Sierra

If it works in the Safe Mode, try running this program when booted normally and then copy and paste the output in a reply. The program was created by Etresoft, a frequent contributor. Please use copy and paste as screen shots can be hard to read. Click “Share Report” button in the toolbar, select “Copy to Clipboard” and then paste into a reply. This will show what is running on your computer. No personal information is shown.

Etrecheck – System Information

Are you trying to access Yahoo mail using Safari or the Mail program?

Mail (El Capitan): Mail troubleshooting

Mail (El Capitan): If you can’t receive messages

Mail (El Capitan): If you can’t send messages

Mail not sending or receiving messages after updating OS X

Safari - Unsupported third-party add-ons may cause Safari to unexpectedly quit or have performance issues

Safari doesn't load a page or webpage items are missing

Web Content not responding