Email is made safe to use by a number of utilities that should be practiced on all machines.
A firewall is a mandatory measure for your machine to be safe while using emails, particularly sketchy emails. One undiscovered or unpatched exploit is all it takes for a hacker to be able to abuse your computer in a variety of ways, most worryingly could be the theft of your personal information (identity, credit card number, social security number, etc.) or loss of data on the computer.
Data Protection Act
The data protection act enforces that the bearer of the data is obliged to keep the data in good hands. This means you data, by law, cannot be abused via e-mail, and anyone who attempts to do is in a breach of the act, therefore liable to be prosecuted.
Securing of personal data
When you send an email, most importantly one with personal or sensitive information, they are encrypted with your digital signature when they are sent to the recipient in order to protect against any unauthorised parties from being able to access and read your e-mail. Your digital signature is tied to your e-mail account and hard-coded to the recipient, so only the recipient should theoretically be able to decrypt the e-mail.