Is there any other safer way to encrypt e$-$mails?

You can use public$-$key encryption. In public$-$key encryption, two keys are created, one key for encoding and the other for decoding.

You can use public$-$key encryption. In public$-$key encryption, two keys are created, one key for sending the message and the other for receiving.

You can use public$-$key encryption. In public$-$key encryption, two keys are created, one key for identifying the receiver of the message and the other for identifying the sender of the message.

You can use private$-$key encryption. In private$-$key encryption, one key is created for the message receiver.