We take reasonable precautions with your data, but you can also follow good practice. First we describe features of our system, then we describe what you can do to keep your data safe.
Your EMail can only be accessed with your password. EMail that you access is set to expire, to prevent caching at your ISP or on the computer that you are using. Additionally, any attempt to access EMail after a period of inactivity will fail. This process can activated immediately by informing the system that have finished accessing your EMail. Should your computer crash or become disconnected from the InterNet, this process will occur automatically, but after a reasonable delay. Should you wish to check your EMail after one hour, you will be prompted again for your password. This only occurs after extended periods of no activity.
Secondly, unscrupulous organisations attempt to "advertise" by sending you unwanted EMail. Any attempt to discourage such "advertising" may generate yet more messages. Such messages are known as "spam" and are typically about money making schemes, pornography and other illegal / unethical scams. Spammers often sell EMail addresses to other spammers at profit and with no regard for your interests - a valid EMail address is the only requisite. Attempts have been made to create a lists of uninterested parties, but these were used for further spamming. For this reason, such messages are blocked by default, but some particularly devious organisations manage to bypass such measures.
Additionally, some organisations "spam" in the name of other organisations, so it cannot be immediately assumed that unwanted messages are from the specified source. It is trivial to forge EMail addresses - this applies to all EMail communication on the InterNet. Important messages should be confirmed via other channels - this applies to all telecommunications.