Several Mac users have reported that they are unable to add email accounts (such as Yahoo or Gmail). The following error message is displayed to users:
Failed to verify the server certificate. This could be because of your network configuration or your proxy settings.
To solve connection insecure pop up on mac then check out below points.
1-Try turning off your antivirus software for a short time. It is known that antivirus software can sometimes make this happen. If this doesn’t solve your problem, keep reading.
2-Expired or revoked SSL certificates may be to blame for this issue. Find and take them away. Here’s what you can do:
a. Start Keychain Access (Applications > Utilities).
b. Choose “My Certificates.”
c. Now, find any certificates that have expired or been taken away. Certificates that are no longer valid will have a red X on them. Find certificates with a red X and the words “This certificate was signed by an untrusted issuer” or “This certificate was signed by an unknown authority.” Delete them when you find them.
d. Restart the Mail app when you’re done.
MAC OS Mail App – How to fix Connection Insecure
You might also get the “connection is not secure” error message if you are using mobile internet and have used up all the data you were given. Check to see if you can still connect to the internet. If you can’t, connect to a Wi-Fi network or call your mobile provider to add more data.
Quit Apple Mail and turn on your Mac again. Turn off Gmail on your Mac, then turn it back on. Take Gmail off your Mac and then put it back on. Take Gmail out of your Keychain and type in your password by hand.
A proxy server is a computer on a local network that acts as a middleman between a single computer user and the internet so that the network can provide security, administrative control, and caching service. Choose Apple > System Preferences on your Mac, then click Network.
If you see the “Not Secure” message, it means that the web page or website you are on does not offer a secure connection. When your Chrome browser connects to a website, it can use either the HTTP (which is not secure) or HTTPS (which is secure) (secure).