OS X Lion: Mail doesn't send certificate-signed message; Compose window cannot be closed
When attempting to send a message in Mail that has been signed by a trusted certificate, a message may briefly appear that states:
"Unable to sign message
You don’t have a trusted certificate in your keychain that matches the email address (sender’s email address). Without a certificate, you can’t sign messages sent from this address."
The message quickly disappears, and the Compose window reappears but cannot be closed.
This message indicates that your keychain contains an invalid certificate for the sender’s email address.
- Quit Mail if it's open.
- Open Keychain Access, located in the Utilities folder, in the Applications folder.
- Click the “Login” keychain in the left column.
- Locate the certificate with the same name as the email address displayed in the message that appeared when the email did not send.
- Remove the certificate from the keychain by pressing the Delete key.
- Open Mail.
- Attempt to send the email message again.
Note: This issue doesn't occur with Mail messages that have signatures, such as your name.
What is a “signed message”?