In recent news, Google announced that it's email service, Gmail, will require all communications to be encrypted using HTTPS (http://www.cnet.com/news/gmail-encryption-is-now-mandatory). So, does using HTTPS mean your email is now secure? The answer is, it depends.
The option to use HTTPS has been a feature of Gmail for some time now. This news simply means that users no longer have an option to opt-out of the secure connections. Using HTTPS with your email provider is a good idea, whether you use Gmail or any other email provider. However, the encryption provided by your email provider usually* ends once the email leaves their servers. At that point, the email travels across the Internet unencrypted.
Despite this news, email is still just as inherently insecure as it's always been. One day that might change. But until then, use Send Files Securely to send secure file attachments.
*Although the technology exists to encrypt email between servers, it's not widely used.