We are often asked about certificate warnings which pop up in email clients. When an account is moved to a new server, there is a new certificate and a new warning often appears. In answer to a question about this:
It’s safe to accept the certificate. We moved your accounts to a newer faster server a few days ago. We had been using a wildcard certificate, but that was causing problems for people running software too dumb or too conservative to work with such a certificate. It seemed like an appropriate time to switch.
Email client software often sets up TLS (encrypted) connections by default. It makes people think sending stuff via email is secure, adding yet another misconception to the rampant ignorance. It’s not secure. Email is a store and forward system. That means your message may cross the network encrypted, but it is then stored unencrypted on the target mail server. It frequently passes through many servers before being delivered. It’s trivial for an administrator of any of those servers to keep a copy – not encrypted.
The security of your message is in the hands of those administrators. You will almost never even know who they are.
Nearly it’s only virtue is that your password is sent over an encrypted connection. It also means that when someone at the NSA wants to read it, he will have to spend a few minutes on a powerful computer to decrypt it first. If you want more secure email, you need to encrypt the content, not just the connection. If you don’t want the NSA or anyone else reading your email at all, you’re basically out of luck.
Content encryption is good enough to deter most criminals and casual snoopers. Unfortunately, a really sophisticated criminal can still decrypt it. But you don’t need to worry about this too much unless you know that your content has a very high value to such a person. If you make it even a little hard, they will move on. There is no shortage of easy targets.
The bottom line is: encrypt the content if you need security. That said, there are better ways to transfer sensitive information than via email. There’s no reason to allow it to have such a high profile. Virtually all cases of hacking are the result of gaping stupid security holes, someone incompetent in charge of security.