Configuring Mail.app to use SSL without the annoying "The root certificate for this server could not be verified" warning.

Mail asks if you want to accept an SSL certificate for each IMAP account. This happens each time Mail opens, even if you click Remember My Decision.

Solution

1. Click "Show certificate" when Mail asks if you want to accept the certificate.
2. Press the Option key while dragging the certificate to the desktop. The certificate's icon appears on the desktop.
3. Add the certificate to your keychain by dragging its icon on top of Keychain Access. Tip: Keychain Access is located in the Utilities folder (/Applications/Utilities).
4. When Keychain Access opens, you may be prompted to select which keychain to import to. If this happens, choose a keychain and also select X509 Anchors.

Additional information

Mail will continue to ask if you want to accept an SSL certificate each time it opens if the certificate is an expired server certificate or is signed by an unknown certificate authority.