I have a certificate that says not trusted which keeps appearing. What should I do about it?

If the Certificate warning relates to a third-party certificate, that secures communication for either a browser session or email account, then the certificate doesn’t exist on your device. As such, there’s nothing to delete.

The warning concerning an untrusted certificate generally indicates one of two security issues:

1) The service to which you are connecting is incorrectly configured - or their security certificate has expired. Your only action is to alert the service provider - who will hopefully try to resolve the back-end issue that you can otherwise do nothing to fix.

2) Alert you to a security issue, whereby your secure SSL/TLS session has been intercepted and decrypted by a “man in the middle” - potentially indicating an attack on your secure communications. If you are using a Corporate IT network, this alert might be expected where their security policy requires inspection of all network traffic.