While the connection between your PC/Mac (not a phone by app by default!!!) is secured using the same encryption technology your bank uses to create a secure connection (Called an SSL)
Once the email you send leaves your provider (e.g. Outlook/hotmail, gmail, yahoo! mail), it's unencrypted straight text which can be pulled from the other of trillions of packets bound for your recipient.
The only true way to insure that the contents of the email remain "safe" are:
1. Using a third party (e.g. Zixmail) where your email is encrypted when it leaves your machine and his hosted on the Third Party's server.
2. Encrypt your email on your machine and then send it onto your recipient and provide them with a decryption utility (PGP)
Short of that, once it leaves your provider, it's fair game.
I work for an financial firm and we go through this all the time and yes, it's a pain, and yes, it's not without problems, but if you want to secure your customers data it's the only way to thwart the "bad guys"
