I recently moved my keys to a different machine and configured Enigmail on the Thunderbird on the new machine. Though I am able to encrypt and decrypt files alternatively in both machine now(which I guess means that the keys got imported to new machine correctly). However now when I send a mail even to myself, I get this message that the signature if UNtrusted. How do I fix this. I have tried to sign my public key myself as some posts suggested but it is saying that the key is already signed by me.
In thunderbird, open the KeyManagement dialog in the OpenPGP menu, then search for your key or hit Display All Keys by Default. Then you can right-click on the key and select Set Owner Trust. There you can set the tust level for the key.
Alternatively, you should get the same option when clicking on Details in the PGP signature area above the message.